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RAILWAY SIGNALING 



BY 

EVERETT EDGAR KING 

MEMBER OP THE AMERICAN RAILWAY ASSOCIATION, SIGNAL SECTION; MEMBER OF THE 

AMERICAN RAILWAY ENGINEERING ASSOCIATION; ASSOCIATE MEMBER OF 

THE AMERICAN SOCIETY OF CIVIL ENGINEERS; PROFESSOR 

OF RAILWAY CIVIL ENGINEERING IN THE 

UNIVERSITY OF ILLINOIS. 



First Edition 



McGRAW-HILL BOOK COMPANY, Inc. 
NEW YORK: 370 SEVENTH AVENUE 

LONDON: 6 & 8 BOUVERIE ST., E. C. 4 
1921 






Copyright, 1921, by the 
McGraw-Hill Book Company, Inc. 



NOV -2 



1^21 



THE :M^PIiK PRESS XORK FA. 



©C!.A630109 



^. I ^ 




f^ 



PREFACE 

It is the purpose of this book to collect from various sources 
that which is already in use in common practice in the field of 
railway signaling and to present it in text-book form suitable for 
the beginner in his study of this subject. Much of the descriptive 
material and many of the drawings were furnished by the various 
signal and supply companies specially for this book. Other 
descriptions and drawings were taken from catalogues and 
descriptive literature issued by these companies. I have not 
included any thing concerning specifications for the construction, 
installation and maintenance of materials. This is a voluminous 
subject in itself; besides, specifications for practically every item of 
equipment that enters into railway signaling are provided for in 
the Manual of the American Railway Association, Signal Section. 

In a few cases, I have quoted from the Proceedings of the 
American Railway Engineering Association, from the Signal 
Dictionary and from the Railway Signal Engineer. As I have 
drawn so largely from the Proceedings of the Railway Signal 
Association, it might be pertinent to state briefly that in its 
early days the organization was known as the Railway Signaling 
Club. Later it changed its name to the Railway Signal Associa- 
tion; and recently during the time when the railways were under 
the supervision of the Director General of Railroads, United 
States Railroad Administration, the organization amalgamated 
with the American Railway Association and took the name which 
it still retains, the American Railway Association, Signal Section. 
I might state in this connection, also, that the Manual and all the 
Proceedings of the organization under both the old and new re- 
gimes may be obtained from the Secretary, Mr. H. S. Balliet, 75 
Church St., New York. 

I want to express my appreciation for the help received from 
all sources, for the material furnished, for the suggestions offered 
and for the corrections made in the preparation of the manu- 
script. I am especially indebted to the Union Switch and Signal 
Company, the General Railway Signal Company, The Federal 
Signal Company, and the Hall Switch and Signal Company for 



vi PREFACE 

the photographs and drawings that I have selected and used for 
general illustrations. I am equally indebted to all the companies 
that have furnished photographs and drawings that illustrate 
their particular line of equipment. I am likewise indebted to 
the Board of Directors of the American Railway Association, 
Signal Section, for permitting me to use the many cuts and quo- 
tations that I have included in the text. I appreciate very much 
the assistance given by Mr. G. A. Blackmore of the Union Switch 
and Signal Company, by Mr. A. G. Moore of the General Railway 
Signal Company, and Mr. S. J. Turreif of the Federal Signal 
Company. I am especially grateful to Mr. Balliet for sugges- 
tions and corrections that he has offered in the preparation of the 
manuscript, and to Mr. S. E. Gillespie for his kindness in prepar- 
ing some of the material for the original manuscript and for 
his valuable suggestions while reviewing and proof-reading the 
major portion of the remainder of it. 

E. E. King. 
Urbana, III. 
September, 1921. 



CONTENTS 

CHAPTER I 

PRELIMINARY 
Art. Page 

1. Introductory , 1 

2. History 1 

3. Organization 2 

4. Rules for Signal Supervisors and Signal Foremen 5 

5. Commissions 7 



CHAPTER II 
SIGNAL INDICATIONS 

6. Two- and Three-position Semaphore Signal Indications 8 

7. Color Lights for Day Indications 11 

8. Position-light Signals 12 

9. Disc Signals 14 

10. Take Siding Signal 17 

11. Relative Location of Signals and Tracks 19 

CHAPTER III 
INTERLOCKING 

12. Definition 22 

13. Object 22 

14. General Plan 23 

15. General Order of Locking Signals and Derails 25 

16. Locking Sheet 26 

17. Diverging Routes 28 

18. Movable Bridge Interlocking 30 

19. Requirements for the Protection of Traffic at Movable Bridges . 32 

20. Track Diagram and Manipulation Chart 35 

CHAPTER IV 
MECHANICAL INTERLOCKING 

Interlocking Machines 

21. General 36 

22. Horizontal Locking 36 

23. Special Locking 39 

24. Vertical Locking 40 

vii 



Viii CONTENTS 

Aht. Page 

25. Special Locking 42 

26. The Dog Chart 44 

27. Stevens Interlocking Machine 48 

CHAPTER V 
MECHANICAL INTERLOCKING 

Other Equipment 

28. Leadouts 49 

29. Pipes and Couplings 50 

30. Stuffing Box 50 

31. Pipe Carriers 50 

32. Compensators 51 

33. Field Construction of Pipe Lines 55 

34. Horizontal Cranks and Radial Arms 57 

35. Crank, Wheel, Compensator, and Pipe Carrier Foundations ... 58 

36. Facing Point Lock 59 

37. Switch and Lock Movement 59 

38. Detector Bar 60 

39. Bolt Lock. 60 

40. Head Rod and Switch Adjustment 62 

41. Lock Rod 63 

42. Derails 65 

43. Crossing Bars 66 

44. Semaphore Signals 67 

45. Dwarf Signals 69 

46. Time Lock 69 

47. Calling-on Arm 73 

48. Movable Bridge Couplers and Locks 74 

49. Rules , 75 

CHAPTER VI 
ELECTRO- PNEUMATIC INTERLOCKING 

50. Air Supply 78 

51. Electricity 80 

52. General Sequence in Power Interlocking 80 

53. Interlocking Machine 81 

54. Mechanism for Throwing Switches and Derails 87 

55. Indication Circuit Controller 90 

56. Indication Relays 90 

57. Detector Locking 94 

58. ''SS" Control 94 

59. Throwing a Switch 94 

60. Signal Operating Mechanism 98 

61. Operating a Signal 99 

62. Advantages 101 



CONTENTS ix 

CHAPTER VII 

ELECTRIC INTERLOCKING 

General Railway Signal Compaxy System 
iRT, Page 

63. Electricity 102 

64. Operating Switchboard 102 

65. Interlocking Machine 103 

66. Switch Lever Wiring 107 

67. Model 2 Sys-itch Machine 108 

68. Model 4 Switch Machine 113 

69. Model 5 Switch Machine 113 

70. Semi-automatic Signal Control 115 

71. Dwarf Signals 118 

72. Cross Protection 119 

73. Alternating-current Interlocking 121 

74. Illuminated Track Diagram 122 

75. Electro-mechanical Interlocking Machine 123 

L'niox Switch and Signal Company Type ''F" System 

76. General 124 

77. Power Supply 124 

78. Interlocking Machine 124 

79. Power Mains 125 

80. The Indicating System 127 

81. Style " M " Switch Movement 128 

82. "SS" Control 131 

83. Auxiliary Features 133 

84. Union "S-7" and ''S-8" Electro-mechanical Interlocking Ma- 

chines 133 

85. Union "P-5'' Electro-mechanical Machine 135 

Federal Signal Company System 

86. Interlocking Machine 135 

87. Type 41 Switch Machine 138 

88. Switch Machine Control and Indication Circuits 141 

89. Federal Electro-mechanical Interlocking Machine 143 

Hall Switch and Signal Company System 

90. Interlocking Machine 144 

91. Switch Movement 145 

92. SvN-itch Operating Circuits 146 

93. Signal Operating Circuits 146 

94. Indication Current 148 

95. Switch Indication Circuit 148 

96. Signal Indication Circuit 148 



X CONTENTS 

CHAPTER VIII 

DIRECT-CURRENT TRACK CIRCUITS 

Art. Page 

97. Track Circuits 149 

98. Cut Sections 150 

99. Fouling Circuits 151 

100. Insulated Rail Joints 151 

101. Rail Bonds for Track Circuits 152 

102. Neutral Relay 152 

103. Polarized Relays 156 

104. Track and Signal Batteries 157 

105. Battery Wells and Battery Chutes 160 

106. Cable and Relay Posts 160 

107. Trunking 161 

108. Insulated Head, Front, and Tie Rods 162 

109. Lightning Arresters 162 

CHAPTER IX 
ELECTRIC LOCKING 

110. Wiring Diagrams for Electric Locks 166 

111. Section Locking 171 

112. Screw Release 173 

113. Clock-work Time Release 173 

114. Approach Locking 174 

115. Route Locking 176 

116. Sectional Route Locking 177 

117. Stick Locking 177 

118. Stick Relay 179 

119. Check Locking 179 

120. Union Electro-mechanical Slot 180 

121. Hall Electro-mechanical Slot 183 

122. Tower Indicators .185 

CHAPTER X 
MANUAL BLOCK SYSTEM 

The Manual Block 

123. General Description 186 

The Controlled-manual Block 

124. General Description 187 

The Electric Train Staff 

125. General 189 

126. Operation of the Absolute Staff Instrument 190 

127. The Permissive Staff 194 

128. Intermediate Siding and Junction Instruments 196 

129. Pusher Attachment 197 



CONTENTS XI 

CHAPTER XI 
AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 

General 

Art. Page 

130. Object 198 

131. Location of Signals 199 

132. Two-position Semaphore Signaling 201 

133. Three-position Signaling 202 

134. Overlap Systems 203 

135. Absolute and Permissive Signaling on Double Track 203 

136. Three-block Indication Scheme 206 

137. Numbering Automatic Signal Posts 206 

CHAPTER XII 

AUTOMATIC BLOCK SIGNALING ON* DOUBLE TRACK 

DIRECT-CURRENT TRACK CIRCUITS 

Normal Clear Signals 

138. Two-position Signal Circuits 208 

139. Two-position Polarized Track Circuits 209 

140. Three-position Signal Circuits 211 

141. Three-position Polarized Track Circuits 213 

Normal Danger Signals 

142. Two-position Signal Circuits 213 

Switch, Curve, and Siding Protection 

143. Switch Indicators , 214 

144. Switch Box • 215 

145. Signals for Outlying Switches and Obscure Curves 216 

CHAPTER XIII 

AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 

AS ALTERNATING CURRENT 

146. Introductory 217 

Single-rail Return 

147. Direct-current Propulsion 218 

148. Impedance Coil 221 

149. Track Transformer 222 

Double-rail Return 

150. Direct-current Propulsion 222 

151. Alternating-current Propulsion 227 

Alternating-current Signaling on Steam Roads 

152. General 227 



xii CONTENTS 

Transformers 

Art. P^qjj 

153. General 228 

Alternating-current Relays 

154. General 230 

Union Switch and Signal Company Designs 

155. Vane Type 230 

156. Ironless Galvanometer Type 231 

157. Iron Core Galvanometer Type 232 

158. Centrifugal Frequency Relay 233 

159. Radial Contact Polyphase Induction Type 234 

General Railway Signal Company Designs 

160. Universal Alternating Current Relay 234 

161. Models 2A and 2B Two- and Three-position Relays 235 

162. Model 2A Two-position Centrifugal Frequency Relay 236 

Alternating-current Track and Signal Circuits 

163. Two-position Signals 237 

164. Three-position Signals 240 



CHAPTER XIV 

Automatic Block Signaling on Single Track 

165. General 249 

166. Union General and Special Plans — TDB System 249 

167. General Railway Signal, General and Special Plans, —A. P. Block 

System 259 

168. Other Installations 262 

CHAPTER XV 
SIGNAL MECHANISMS 

Two-PosiTioN Signals 

169. Hall Disc Signal 271 

170. Union Style "B" Signal 272 

Three-position Signals 

171. Union Electro-pneumatic Signal 275 

172. Union Style "S" Signal 275 

173. Union Style ''T-2" Signal 276 

174. General Railway Signal Model "2A" Signal 279 

175. HaU Three-position Style "K" Signal 283 

176. Hall Style ''L" Signal 284 

177. Federal Three-position Type -'4" Signal 285 



CONTENTS xiil 

Automatic Stops 

Art. Page 

178. Motor-operated Automatic Stops . 288 

Light Signals 

179. General 288 

Color-light Signals 

180. Long-range Type 291 

181. Medium-range Outdoor Type 293 

182. Short-range Subway and Tunnel Type 297 

Position-light Signals 

183. Long-range , 299 

184. Short-range or Dwarf 301 

CHAPTER XVI 
HIGHWAY CROSSING SIGNALS 

185. General 302 

186. Highway Crossing Signals 302 

187. Highway Crossing Signal Circuits 305 

188. Interlocking Relay 306 

189. Hoeschen Bell System 308 

190. AGA Highway Danger Signals 315 

APPENDIX A 

Rules Governing the Construction, Maintenance and Operation of 

Interlocking Plants 318-324 

APPENDIX B 

Part I 
Signal Aspects 325-327 

Part II 
SjTiibols Recommended by the Railway Signal Association .... 328-340 

APPENDIX C 

A Definition of Terms Used in Railway Signaling 341-362 

Index 363 



1 



RAILWAY SIGNALING 



CHAPTER 1 
PRELIMINARY 

1. Introductory. — Practically the only purpose a railroad has 
is to give train service to the public and its industries; and 
whatever will facilitate and expedite train movements to the best 
advantage to serve this purpose with a reasonable expenditure of 
capital will work to the best interests of the public generally. 
As the number of trains increases and their speed, weight, and 
length grow greater in the effort to handle the continually increas- 
ing volume of traffic, the demands for safe and efficient methods 
of train operation become more urgent. A great many factors 
enter into the success of railroad transportation, among which 
are the motive power and train equipment, the track and road- 
way, the signal systems and methods of despatching trains, and 
the personnel of the employees from the office boy to the manager. 
This text deals only with signaling; and the reader should bear 
in mind that signaling is a means to an end and not the end 
itself. 

2. History. — An early history of railway signaling in America 
written by Mr. J. A. Anderson and published in the March 5, 1909 
issue of the Railway Age Gazette and reprinted in the 1909 Volume 
of the Proceedings of the Railway Signal Association, gave 1870 
as the date for the first interlocking plant and 1863 as the date 
for the first block system. The interlocking plant was installed 
at Trenton, N. J., on the line of the United New Jersey Canal 
and Railroad Companies, afterwards leased by the Pennsylvania 
Railroad Company. The machine was built by Saxby and 
Farmer of London after the same pattern as those they had built 
and installed on lines in England. It was built principally as 
an experiment, and from this humble beginning the interlocking 
plant has been installed wherever important railroad crossings 
and terminals have been established. 

1 



2 RAILWAY SIGNALING 

The block system was introduced by the same company on the 
line between New Brunswick and Philadelphia. A form of block 
signaling had been proposed in England as early as 1842, but its 
adoption in that country generally was very limited for a number 
of years afterwards. The system established in America gave 
positive indications by means of signals, and went a long way in 
eliminating many of the difficulties involved in the older foreign 
systems. » 

In the early days practically all of the signal appliances were 
of a mechanical type, more or less simple in construction, and 
did not require men especially trained for their maintenance 
and operation. Improvements were made from time to time to 
keep pace with the demands of transportation. The public 
saw in signaling possibilities for greater safety; the railroads saw 
opportunities for both safety and efficiency in operation. Later, 
electricity was applied to solve the signal problems, and it became 
a potent factor in the growth of the signal industry. More and 
more was it utilized to replace the human element in signal 
operation. As the systems grew, organizations grew with them. 
As the equipment became more complicated, there came the 
demand for specialists, men who were better trained, and who 
could give all their time and attention to this particular kind of 
work. Power interlocking was introduced and the track circuit 
became well established. Gradually a reliable system has thus 
been developed to meet the needs of the situation. Interlocking 
appliances have been made better and automatic block systems 
perfected until accidents rarely occur on account of signal 
failures. The service has been so improved that many roads 
have been able largely to eliminate the train order as a factor in 
despatching trains. 

3. Organization. — The field of signal engineering is a distinct 
one and embraces construction, installation, operation and 
maintenance of railway signals. The equipment is practically 
all made by signal manufacturers and is bought by the railroads 
at a unit price or on a contract basis. The companies that make 
the equipment may also install it, or the railroad may take the 
equipment when it is delivered and install it with its own con- 
struction forces. In nearly all cases the maintenance is handled 
byjiailroad forces. 

The general type of organization that prevails on a road will 
determine, in a measure at least, the particular organization of 



PRELIMINARY 3 

the signal department. In the departmental system, the signal 
engineer reports to the chief engineer and has charge of all the 
work of the signal department. He makes requisitions for new 
equipment, has charge of all materials and supplies on hand and 
directs the work of the organization. In the divisional system, 
the signal engineer reports to the chief engineer as before and has 
immediate charge of standards and construction. The divisional 
maintenance is in charge of the signal supervisor who reports 
directly to the division superintendent or division engineer. In 
this connection he is assisted in an advisory way by the signal 
engineer. The following article written by Mr. A. G. Shaver 
and published in the September, 1917, issue of the Signal Engineer 
states some of the requirements for success as a signal engineer 
and outlines a typical signal department organization:^ 

"Four qualifications are indispensable in every man that he may be 
a good signal engineer; he must have had experience in railway signal- 
ing; he must have a technical education; he must be a good executive, 
and he must have a general knowledge of railroading. Any signal 
engineer who does not have an intimate knowledge of signaling, such as 
one gets from actual service as laborer, skilled workman, foreman or 
maintainer, is not only greatly handicapped, but is more or less inefficient 
to his company. The technical education need not be that acquired by 
a course in college, though that is an advantage; it must include a 
very complete knowledge of the general principles of electricity, an 
understanding of mechanics and a famiharity with those features of 
civil engineering concerned in railroad construction. Since the job of 
signal engineer on most railroads carries with it a command over men, 
executive ability is necessary for effective results. In railroading a 
knowledge of construction, maintenance and operation is needed. The 
construction of the railroad and the signaHng must harmonize and be 
maintained and operated together; it is particularly necessary to know 
how trains are" run and what the facilities must be for trains to be 
operated to the best advantage. 

"Signal departments vary considerably in make-up and jurisdiction, 
having often been gradually built up from some old arbitrarily estabUshed 
basis and having to meet conditions peculiar to the railroad itself. 
There are, doubtless, few signal department organizations entirely 
satisfactory to the signal engineer in charge. 

''An example of a suitable signal department organization for a large 
road is shown by the diagram Fig. 1. The assistant signal engineer, 
the general inspector, the superintendent of signal construction, the chief 

1 Page 276. 



4 RAILWAY SIGNALING 

draftsman and the chief clerk all report to the signal engineer. The 
assistant signal engineer is in authority next to the signal engineer and 
has charge of all matters pertaining to maintenance and operation and 
the preparation of standards and specifications. The general signal 
inspector has supervision over all inspections, investigations, tests, 
experiments, educational matters and the signal shop. The superin- 
tendent of signal construction has charge of all work of construction, 
reconstruction and changes. The chief draftsman has the preparation 
of estimates and drawings, the designing of circuits and apparatus and, 
under the assistant signal engineer, the making of standards and speci- 
fications. The chief clerk has authority over the force and business 
of the office, including accounts, statistics, reports, payrolls, etc. The 

I Signal Engineer | 



I Chief Clerk | 
I Office Force | 



Asst, Signal 
Engineer 



General 
Inspector 



I Superintendent | 



I Inspectors | | Tests 
[" Signal Shop | 



Educational 
Work 



Signal 
Supervisor' 



Supt. Signal 
Construction 



Chief 
Draftsman 



Construction 
Foremen 



Drafting 
Force 



Construction 
Forces 



Maintenance 
Forces 



|Towermen] 



Fig. 1. — A typical signal department organization. {Railway Signal Engineer.) 

signal supervisor reports to the superintendent in all matters pertaining 
to the maintenance and operation of signals and to the assistant signal 
engineer on technical matters, special reports, special requisitions and 
those things not covered by standards and approved practices; he is 
appointed by the superintendent on approval of the signal engineer. 
The signal engineer gives to the superintendent general and special in- 
structions concerning maintenance and operation of signals, confers 
with him regarding new construction proposed and authorized and as- 
sists to get efficient results from the signaling in service. 

"On a small railroad this organization may be varied to suit condi- 
tions. Ordinarily the signal engineer would have direct authority over 
the maintenance and operation of signals as well as construction and 
other matters, and his organization might be curtailed as to the number 
and assignment of subordinates. Indeed, a railroad may be so small, 
as to the amount of signaling it has, as not to need a signal department 



li 



PRELIMINARY 5 

at all. The care of its signal work could be given over to some existing 
department having work of a like nature and expert service hired as 
required." 

4. Rules for Signal Supervisors and Signal Foremen. — In 

order to establish a high grade of uniform practice among signal 
supervisors and their foremen, the following rules were prepared 
and written in the Manual of the American Railway Engineering 
Association:^ 

Rules Governing Signal Supervisors 

1. Signal Supervisors shall report to and receive instructions from the 

(Title) 

2. They shall be responsible for the safe condition and proper maintenance 
of signals and interlocking plants. They must make temporary repairs 
of such defects as may endanger or delay the movement of trains, and 
promptly report defective conditions to the .(.T.!^!.?.l 

3. They must make frequent inspections of signals and interlocking plants 
and have necessary repairs made as promptly as conditions require. They 
must see that all failures of signals and interlocking plants are promptly 
investigated and report made on Form No 

4. They shall, as necessary, employ men for carrying out the duties for 
which they are responsible. 

5. They must know that foremen are familiar with the operating rules 
in regard to train signals and flagging, and that they fully understand and 
comply with them. 

6. They must, in case of damage to signals or interlocking, promj)tly as- 
semble forces, tools and materials, and make necessary repairs. 

7. They shall investigate and report on accidents which may be attri- 
butable to defects in, or result in damage to, the signal apparatus. 

8. They shall conform to the prescribed standards and plans in the execu- 
tion of work under their charge. 

9. They must know that foremen are supplied with tools and materials 
necessary for the efficient performance of their duties, and see that these 
are properly used and cared for. 

10. They must not, except by proper authority, permit experimental 
trials of appliances or devices, nor give out information of the results of 
any trial. 

11. They shall keep themselves informed in regard to all work performed 
in their districts by contractors, or others who do not come under their 
charge, see that nothing is done by them that will interfere with the safe 
operation of signals, and report promptly to the (T^.^.^®} 

if the work is not done in accordance with the prescribed standards. 

12. They shall have immediate supervision of work-train service for the 
■maintenance of signals and interlocking plants in their districts, and em- 
ploy such service only when authorized by the (.T.iy.^.). 

1 Page 430, 1915 edition. 



6 RAILWAY SIGNALING 

13. They must know that foremen are provided with the rules, circulars, 
forms, special instructions and safety regulations pertaining to their duties, 
and that they fully understand and comply with them. 

Rules Governing Signal Foremen 

1. Signal Foremen shall report to and receive instructions from the 

(Title) 

2. They shall be responsible for the proper inspection and safe condition 
of signals and interlocking plants under their charge, and shall do no work 
thereon that will interfere with the safe passage of trains, except under proper 
protection. 

3. They must make such inspection of the signals and interlocking plants 

in their districts as the ffl.^i?.). may direct, and report 

all defects found on Form No. 

4. They shall employ men as the ITA^J.^.}. directs. 

They must treat employees with consideration, and see that they properly 
perform their duties. They must discharge men who are incompetent or 
neglect their duties, but in no case shall they discharge men without cause. 
They must keep the required records of the time of their men and of the 
materials used. 

5. They must each have a copy of the current timetable, and be thor- 
oughly familiar with the rules and regulations therein, and with the time 
of trains over their districts. They must carefully observe signals dis- 
played by all trains, and assure themselves, before obstruct ng track, that 
all trains and sections due have passed. No notice will be given of extra 
trains, and employees must protect themselves as prescribed by the rules. 
Foremen must provide themselves w^ith reliable watches, and, when pos- 
sible, verify time daily with a standard clock or with the watches of other 
employees who are required to have the standard time. 

6. They must, in case of damage to signal or interlocking apparatus in 
their districts, promptly proceed to the place with the men, tools and mate- 
rials at their command and do all in their power to make necessary repairs. 

7. They shall investigate and report on accidents which may be attri- 
butable to defects in, or result in damage to, the signal apparatus. 

8. They shall conform to the prescribed standards, plans and specifica- 
tions in the execution of the work under their charge. 

9. They shall be responsible for the proper care and use of tools and mate- 
rials necessary for the efficient performance of their duties, and shall make 
requisition to the .(T.!!".!.^.? from time to time as additional 
supply becomes necessary. 

10. They must not, except by proper authority, permit experimental 
trials of appliances or devices, nor give out information of the results of 
any trial. 

11. They must not make nor permit any permanent rearrangement or 
change in the signals or interlocking plants without proper authority. 

12. They must thoroughly understand the rules, circulars, forms, special 
instructions and safety regulations pertaining to their duties, and see that 
they are complied with. 



I 



PRELIMINARY 7 

5. Commissions. — The Interstate Commerce Commission and 
State Railroad or Public Utilities Commissions are vitally inter- 
ested in railway signaling, but their interest lies wholly on the side 
of safety. In its early days the Interstate Commerce Commis- 
sion gave attention to investigations concerning safety in signal 
systems, and in 1907 it established a Block Signal and Train 
Control Board. This Board was charged with a number of 
duties, among which were those of making investigations in 
regard to block signals, automatic stops and cab signals, and other 
devices that were produced with the idea of promoting safety in 
railroad operation. As block signals had been in service for a 
sufficient period to be made successful in operation, the Board 
gave a large share of its attention to automatic stops and cab 
signals. For a number of years automatic stops have been used 
on subway, elevated and other electric lines, but their application 
has not yet been extended generally to steam roads. The Block 
Signal and Train Control Board passed out of existence in 1912, 
and their work was then handled by the Division of Safety of the 
Interstate Commerce Commission. In 1917 the name of the 
organization was changed to Bureau of Safety of the Interstate 
Commerce Commission. 

Many of the state commissions have formulated rules govern- 
ing the installation and operation of interlocking plants, block 
signal systems and other appliances, and have a corps of inspec- 
tors to see that their requirements are fulfilled. One of the im- 
portant problems that the state commissions have to face is the 
question of adequate protection for vehicles where the highways 
cross the railways at grade. This has become especially serious 
in recent years on account of the heavy increase in automobile 
traffic over transcontinental and other high-speed routes. 



CHAPTER II 
SIGNAL INDICATIONS 

Signals are used to convey certain information to trainmen 
and others interested in railway operation that they may be able 
to act intelligently with safety and promptness concei^ning train 
movements. Practically all of the information given by signals 
is intended for enginemen, and is generally conveyed by visual 
indications. ** Railway Signaling" is, then, that branch of rail- 
way service that is engaged in installing and operating such 
equipment and appliances adjacent to the track as will indicate to 
an engineman whether he should advance his train or stop it. 

6. Two- and Three-position Semaphore Signal Indications. — 
The day indications are given by different positions of semaphore 
arms, by colored and uncolored lights, or by discs; while night 
indications are given entirely by colored and uncolored lights. 
Signal indications may be either two-position or three-position. 
Two-position signals require a home and distant signal. The 
home signal gives final authority to the enginemen while the dis- 
tant signal merely repeats the indications of the home signal; 
and its function is purely cautionary. 

In two-position semaphore signaling the home blade is made 
with a square end for interlocking and with either a square end 
or a pointed end for block signaling. The front of it is usually 
painted red with a white stripe near its outer end and the back of 
it white with a black stripe near the end. The distant blade is 
made with a V-shape or fish-tail end. The front of it is generally 
painted yellow with a black stripe parallel to the end of the blade, 
or green with a white or red stripe. The back of the blade is 
painted white with a black stripe. A few roads that do not use 
this notation, paint the front of all blades yellow with a black 
stripe and the back black with or without a white stripe. 

Three-position blades are made with square ends for inter- 
locking purposes and with either square or pointed ends for block 
signaling. Wliere both square and pointed blades are used, the 
square end blades indicate stop and stay when the signal indicates 
stop; while the pointed end blades indicate stop and proceed at 



SIGNAL INDICATIONS 



9 



low speed when the signal indicates stop. Stop and stay is al- 
ways the stop indication at interlocking plants. 

The front side of three-position blades is painted red with 
a white stripe parallel to the end or yellow with a black stripe. 
The back side is painted white with a black stripe, or black with 
or without a white stripe. 

Signal blade indications are given in either the lower or upper 
quadrant. Two-position signals built as such generally operate 
the blade from the horizontal into the lower quadrant. In the case 
of the home signal, the horizontal position means stop; the 
inclined position, which varies from 45 to 75 degrees below the 
horizontal, with an average of 60 degrees, means proceed. In the 
case of the distant signal, the horizontal position means caution 



/?<?^ 




Fig. 2. — Two-position home signal. 



and indicates that the home signal is in the stop position; the in- 
clined position means proceed and indicates that the home signal 
is in the proceed position. An engineman may pass a distant 
signal set at caution, but he must be prepared to stop at the home 
signal set at stop. In the case of interlocking, he must stop and 
stay, while in some cases in block signaling he may proceed after 
the stop. Figures 2 and 3 show the ordinary two-position home 
and distant semaphore signals. 

Three-position signals may operate the blade in either the 
lower or upper quadrant. The horizontal position means stop; 
inclined up or down 45 degrees from the horizontal means cau- 
tion, the first signal ahead is at the stop indication; up or down 
90 degrees from the horizontal means proceed. Figure 4 shows 
three-position lower and upper quadrant semaphore signals. 

The upper quadrant signal is the latest development of blade 



10 



RAILWAY SIGNALING 



indications and possesses some advantages over lower quadrant 
movements, chief among which is the fact that the arm does 



Ye/hyi^ 




^K 




Green 



Fig. 3. — Two-position distant signal. 

not require a counterweight to place it in the stop position. 
This is of considerable importance in case of failure of signal 




Yellow 






Yeliow 




ereen 



Fig. 4. — Three-position lower and upper quadrant signals. 



operating mechanisms. Should sleet collect on the blade it would 
tend to pull the upper quadrant signal to the stop position and 



SIGNAL INDICATIONS 11 

to hold the lower quadrant signal in the proceed position. There 
is little doubt, too, but that the blade giving the proceed indi- 
cation in the upper quadrant can be seen farther by enginemen 
than one giving the same indication in the lower quadrant. 

Signal light indications in the case of two-position signals are 
given by two colors in the home and two in the distant signal. 
A red light in the home signal means stop, a green light means 
proceed, as indicated by Fig. 2. A yellow light in the distant 
signal means caution, a green light means proceed, as shown by 
Fig. 3. Some roads use the combination red and white, and 
green and white, for the indications. The objections raised 
against the white light are that it might be confused with some 
other light or might be the result of a broken roundel. In the 
case of three-position signals a red light means stop, a yellow 
light caution, a green light clear, as indicated in Fig. 4. Some 
roads use the combination red, green, and white, but the same 
objections hold against the white light. Where three-position 
signals are used at interlocking plants, not in block signal territory, 
the home and distant signals are wired to indicate only in the 
and 90-degree positions, upper and lower quadrants. When 
used where automatic block signals are in operation, the home and 
distant signals indicate also in the 45-degree position, a caution 
indication for block signaling, but proceed for interlocking. 

The casting in the two-position signal is generally made with 
three spectacles in which the upper two glasses, called roundels, 
are the same color. The object of having the two glasses with the 
same color is to give a continuous stop or caution indication 
until the signal reaches the proceed position. The three-position 
lower quadrant signal frequently has four spectacles, the extra 
one being made to provide for two possible positions of the signal 
lamp. Usually the lamp is on the side of the post, but occasion- 
ally it stands on top. 

7. Color Lights for Day Indications. — Within recent years it 
has become the practice on many electric lines and even on some 
steam roads to use lights for giving both day and night indica- 
tions. Where large and powerful lenses are used in connection 
with reflectors and deep hoods, as shown in Fig. 5, the lights can 
be seen for a considerable distance, even in bright sunlight. For 
three-position signaling with colored lights each signal will have 
three lenses, red, yellow, and green, placed vertically with the 
usual arrangement of having the red at the bottom, the yellow 



12 



RAILWAY SIGNALING 



in the middle, and the green at the top. The range of vision 
varies from a few hundred feet for subway and tunnel signaHng to 
3,000 ft. for outdoor signaling where the light must be distinctly 
seen in bright sunlight by high-speed trains. There must be 
enough spread to the light so that a train crew can readily see it 
as they approach it on a curve. 




Fig. 5. — Color-light signal. 



8. Position-light Signals. — The position-light signals first came 
into use in 1915 at the time the Pennsylvania Railroad elec- 
trified its line between Philadelphia and PaoH. The signal is a 
modification of the semaphore to the extent that the indications 
are given by electric lamps placed in rows to represent the positions 
of the blade in upper quadrant signaling. Both two- and three- 
position signals are used for high-speed lines with four lights in 
each row spaced 18 in. apart to represent the different positions 
of the signal blade. Yellow-tinted lenses are used with the 
advantage of having a longer range of vision. The lamps for 
high signals are provided with deep hoods and with metal back- 
grounds. The dwarfs are provided with two lunar-white lamps 
in each row constructed for a comparatively short range of vision. 

Light signals require a greater current than semaphore signals 



SIGNAL INDICATIONS 



13 



for continuous normal clear indications, for it requires a compara- 
tively small amount of energy to hold semaphores to the proceed 
indication; but if Hghts could be wired to give their indications 
only on the approach of trains, they would use a very small 
amount of current and extend the life of the lamp in proportion. 
There is more justification for using lights to give day indications 
on roads that use alternating current for signaHng or propulsion 
than on those that use the battery for signaling. As the current 
is already available in those cases, practically no additional expense 
is necessary for wiring. 




Fig. 6. — Position-light signal. 



As there are no complicated mechanisms nor moving parts as 
there are in the case of the semaphore signal, the chances for 
failure are materially reduced. By having standard light indica- 
tions for both day and night signaling instead of two distinct 
types, the semaphore for position by day and the light for color by 
night, the system becomes much simplified. The lights have 
another advantage that there are no exposed parts, such as the 
disc or blade to collect sleet and ice, thereby tending to obscure 
the indication. The following conclusions concerning the use of 
light signals are given in the 1917 volume of the Proceedings of 
the Railway Signal Association:^ 

1 Page 10. 



14 RAILWAY SIGNALING 

First. — Colored and position-light signals, for day and night use, by 
elimination of all moving parts except the control relays, reduce the 
number of failures. 

Second. — Light signal aspects have greater visibility and range under 
adverse weather and background conditions than the semaphore, while 
the close indications compare favorably. 

Third. — ^Light signals give uniform indications at all times. Other 
types of signals give the indication by position in daylight, by color at 
night, and by both during transition periods. The various aspects of 
the position-Ught signal are equal in intensity, range and visibility. 

Fourth. — In general practice, the number of aspects of any one arm of 
a semaphore is limited to three. With the position-light signal, four 
distinctive positions may be used, while the number of indications 
given by colored-light signals is limited only by the colors available. 

Fifth. — Where power is available, the cost of operating light signals 
is less than for operating motor signals. 

Sixth. — Current consumption under normal automatic signal condi- 
tions : 

Position-light signals: Four 5-watt lamps — 20 watts. 

One colored light : 35 to 50 watts. 

For interlocking signals, consumption is increased depending upon 
the number of lights displayed, but the ratio holds. 

Seventh. — Cost of maintenance of light signals is considerably less 
than that of motor signals, and, as the colored-light signal has fewer 
lights to renew, it has an advantage in this respect over the position- 
light signal. 

Eighth. — The field for the economical use of light signals is limited, 
as noted above, to points where power is available. In this field, the 
light signals have advantages over other types. The position-light 
signal can be installed at any location where clearance will permit the 
present standard semaphore to be erected. The colored-Hght signal can 
be used in more restricted clearances. 

9. Disc Signals. — A few roads are using the disc signal for 
automatic block signaling purposes. It operates as a two- 
position signal, although in an entirely different manner from the 
semaphore type. The day indications are given by colored discs, 
a red disc for the home signal and a yellow or green one for the 
distant signal. Each disc operates in an enclosed case mounted 
on top of a post that stands in the same relative position to the 
track as does the semaphore signal, as shown in Fig. 7. To give 
the stop or caution indication, the disc swings into full view 
entirely covering the opening in the front of the banjo-shaped 
case, as shown by (a) and (6) of Fig. 8. To give the proceed 



i 



SIGNAL INDICATIONS 



15 




Pjq, 7_ — Disc signals arranged for left-hand running. 





Fig. 8. 

(a). Home Signal, 

Stop Indication, 
Red Disc, 
Red Light. 

(c). Home Signal, 

Proceed Indication, 
No Disc, 
White Light. 



-Disc signals. 

ib). 



Distant Signal, 
Caution Indication, 
Yellow or Green Disc, 
Green Light 



(a). Distant Signal, 

Proceed Indication, 
No Disc, 
White Light. 



16 RAILWAY SIGNALING 

A.C.L.ond B.a O.R.R. N.C a S.T.L.R.R. 



<^g Wh)f2Lfght 
Normal Take S'ldmg 



'^^No Light 
P) or Letter 



Bg Day -Whits 
Letter "S" 
\duNight-WhHti 
) Letter "S" 
I/fuminated 



Normal Take Siding 



ID K^ 



M. C. R. R. 



^ [^ 



4) ^ k.k 

%c pamted Bhck\ \ 



R}u Day-Wihhing 
%llow Lightarfit 
^ Tntermifterjt Whits 



^•i ^ ;^ ^o) (.Q 

No Light. Disc painted Black 

Normal Freight Take Siding 

q. a c R. R 



QlBuNight-Wmking 
^ryifellow Light ^ 



<^ 



Red 

Light^ 

Stop 



Red 



S 



Red 






=i| Liffi^tJiin 

lU+ic 

:.c. 

v9 



!r 



Cau+ion Clear 

C.C.C & S T L RY 



Green ^ 
Light ~Y/\ 

Take Siding 



^ 



Normol 

A.T. aS.F.RY 



No Light or Letter -, 
Normal Normal 

MO.PAC 



Green y\^ YelloW( 
Light C\\ Light^ 



ByDag-White 
Letter "S" 



(^By Night-White 
^ Letter. "S" 



Illuminated 



Yellow 
Lighted 



Normal 



-White Ught 
Take Siding 



Continue on 
Main Track 



Green 
^i9ht(V\ 



En+er5idini 



Take Sidinc 



Yellow 
Light 



at First 5w 



iding 
witch 



yellow 
Ligfit , 



Proceed on Main 
Track with Caution 



OO 
O OJ 



P R R 






32. 



o o 



KL 



O O 



'No Lights 



'^No-glare 
iahts 



Normal 



Take Siding 



Fig. 9. — Take siding indicators. 



W<7 Lights 

Normal 
{Fro. R. S. A. 



S No-glare Lights 

Take Siding 
1918, vages 276-277.) 



^1 



SIGNAL INDICATIONS 



17 



indication it swings almost, if not entirely, clear of the opening 
as indicated by (c) and (d) of Fig. 8. Just above each disc is a 
light for the night indications that are given by the following 
colors: (a) red; (b) green; (c) white; and (d) white. Where two 
discs appear on one mast, the upper one is generally the home 
signal and the lower one the distant signal. 




Fig. 10. — R. S. A. take siding signal. 

10. Take Siding Signal. — The take siding signal in one form or 
another is used by a few roads to notify trainmen without the use 
of train orders to take siding at non-interlocked switches, espe- 
cially located at some distance from the operating towers. The 
different types include both semaphore arms and discs. One of 
the forms in service is a two-arm signal in which the lower arm is 
2 



18 



RAILWAY SIGNALING 




Fig. 11. — Ground signals. 




Fig, 12. — Signal bridge. 



SIGNAL INDICATIONS 



19 



operated to the 45-degree position in the upper quadrant and is 
marked with the words " Take Siding" illuminated at night. One 
road employs a disc case that displays a swinging disc for day 
indications and a blinking light for night indications. Two 
roads use a disc bearing a white letter ''S" illuminated at night, 
and two use a yellow disc bearing the words ''Take Siding'' 
properly illuminated at night. Another road employs five no- 
glare lights arranged in the form of an X for both day and night 




Fig. 13. — Bracket signal. 



indications. The signal is located in the rear of the switch, so 
that the engineman must pass it before he takes the siding. It is 
controlled from the nearest tower or from the train despatcher's 
office, and is usually operated by means of the ordinary electric 
signal mechanism. 

11. Relative Location of Signals and Tracks. — There must be a 
set of signals to govern the movements of trains in each direction. 
In railway practice in America, ground signals are nearly always 
located on the right-hand side of the track they govern, as indi- 



20 



RAILWAY SIGNALING 



cated by Fig. 11. On one or two double-track roads where left- 
hand running is the custom, they are located on the left-hand side. 
In the case of semaphore signals, on steam roads, the blade 
extends to the right of the post while on electric railways, the 
blade may extend either to the right or to the left, depending 
upon local conditions. Where there are several parallel tracks 
or where there is not sufficient room at the side for semaphores, 
the signals are usually mounted on signal bridges. In this case. 




Fig. 14. — Bracket signal and doll post. 



they are mounted on short poles, supported above or suspended 
below the bridge directly over the tracks they govern, as shown 
in Fig. 12. 

Where there are two high-speed tracks for traffic in the same 
direction, as in the case of the four-track line, the bracket signal 
may be used as shown in Fig. 13. The inside signal governs 
the inside track of the two and the outside signal the outside 
track. If the outside track is a freight line where trains are run 



SIGNAL INDICATIONS 



21 



at a somewhat lower speed, the outside pole may be a little shorter 
than the inside one. 

In case there is a siding between the high signal and the track 
it governs, the bracket type of semaphore may be used as before. 
A bracket post signal will govern the inside track and a short doll 
pole without a signal blade will represent the outside track. 
This arrangement is simply to indicate that there is one track 
between the signal and the track it protects as shown in Fig. 14. 
A purple light is used on the doll pole at night. If there are two 
tracks between the signal and the track it governs, two such doll 
poles will be used on a bracket post. 




Fig. 15. — Upper quadrant two-position dwarf signal. 



Dwarf signals are used as home signals to give interlocking 
indications in practically the same manner as high signals ex- 
cept that they are used only where the movements of trains are 
slow. The dwarf is not used at all for block signaling purposes, 
neither is it used as a distant signal. An upper quadrant two- 
position dwarf signal is shown in Fig. 15. It is the practice on 
many roads to use the purple instead of the red Hght for dwarf 
indications. This is distinctive; and, although of short range, 
it is possible to use the purple since the train movements that 
it governs are necessarily slow. 



CHAPTER III 
INTERLOCKING 

12. Definition. — The subject of signaling naturally divides it- 
self into two phases, interlocking and block signaling. As dis- 
cussed here, interlocking is the operation of an assemblage of 
equipment and appliances used to govern the movements of 
trains over conflicting routes; while block signaling is the opera- 
tion of equipment and appliances used to govern the movements 
of following or opposing trains over the same route. 

Where movements of trains on one track may conflict with 
those on another, such movements are usually governed by visi- 
ble signals operated by an interlocking mechanism so constructed 
and arranged that there can be no conflict of signal indications. 
This not only provides safety for train operation, but also expe- 
dites train movements. Such "an arrangement of switches, lock 
and signal appliances, so interconnected or interlocked that one 
movement must succeed another in a predetermined order," is 
defined by the American Railroad Association as an interlocking 
plant. 

13. Object. — The plant is so constructed that the control of 
all the ground functions is located at one point. This provides 
for a much more expeditious operation than if each function had 
to be manipulated by a lever on the ground. The control equip- 
ment usually is placed in the second story of the tower, which is 
so located and constructed as to permit the operator to see the 
entire yard. Concentrating the controlling apparatus all at one 
point provides an opportunity for interlocking that would be 
almost impossible if each function were handled as a separate 
unit. 

Up to 1919 there had been installed approximately 5,300 
interlocking plants on American roads. The motives that 
prompted expenditures for such equipment were based on the 
idea of expediting train movements while assuring their safety. 
At a railroad crossing where no interlocking plant is installed, 
all trains in most states are obliged by law to come to a full stop 
before they attempt to pass the crossing. The purpose of such 
regulation is to require train crews to ascertain that the way is 

22 



INTERLOCKING 23 

clear in order to prevent collision, and even then there is a strong 
possibility of trains colliding. If there should be a number of 
such crossings in succession in regions of dense traffic, the time 
lost in stopping and starting would tend to intensify the conges- 
tion that might arise from other sources. Where interlocking 
plants are installed at crossings, however, trains are not ordinarily 
required to stop. This affects a saving not only in the time ele- 
ment involved, but also in the expense of operation in stopping 
and starting the trains. In 1905, Mr. J. A. Peabody, Signal 
Engineer for the Chicago and North Western Railway Company, 
obtained some analyses of the cost of starting and stopping 
trains; and from the data then available he determined that a 
road could economically install an interlocking plant where there 
were between 16 and 20 trains a day.^ While the first cost of 
construction and the expense of operation of such plants have 
increased since that time, the expense of train service and equip- 
ment has increased in proportion so that the conclusions drawn 
probably still hold true. 

In the case of four-track lines where two tracks are ordinarily 
given to passenger service and two to freight, the capacity of the 
road may be considerably increased if the crossovers between 
tracks having traffic in the same direction are interlocked. This 
arrangement would permit a fast freight, for instance, safely to 
take the passenger track between two points in order to pass a 
slower freight without the necessity of the slower train taking 
siding and waiting. 

14. General Plan. — The first step in installing an interlocking 
plant is to make, or otherwise secure, a plan of the tracks affected. 
This should be drawn to suitable scale and should show all tracks, 
switches, and railroad crossings, and all street crossings, buildings, 
tanks and water-cranes that may influence the details of the 
plant. The size of the scale will depend upon the complications 
and local conditions, and will usually be 100 ft. to the inch. Fifty 
feet to the inch may be chosen if greater detail is necessary. 
The tower, signals, derails, and other parts of the interlocking 
plant are then located on the map using for this purpose the sym- 
bols adopted and recommended by the Railway Signal Associa- 
tion, and which are shown in Appendix B. It will be noted that a 
signal is laid flat on the map with the top in advance of the base 
as the train it governs approaches it. 

1 Proceedings Railway Signal Association, Volume I, 



24 RAILWAY SIGNALING 

Two sets of signals are required for an interlocking plant, a 
home signal and a distant signal. The home signal stands just in 
the rear of the derail or switch that it governs; while the distant 
signal stands from 1,200 to 6,000 ft. in the rear of the home 
signal. The distance between the two signals depends upon the 
length of track required to stop a train and the kind of power used 
to operate the distant signal. The home signal is the controlling 
one and must not be passed by a train until the proper indication 
is given. The distant signal is a purely cautionary function and 
serves to warn enginemen of the indication that its home signal 
is showing at that particular time. 

On account of the heavier train equipment and the high 
speed found necessary to maintain schedules, many roads that 
formerly operated their distant signals mechanically with a wire 
have moved them farther away from the home signal and are 
operating them by electric power. This increased distance 
affords greater safety in train operation with but little, if any, 
more expense for maintenance. From a questionnaire sent out 
by the Railway Signal Association in 1906 it was found that for 
15 roads, approximately one-third of the mileage in the United 
States, the average distance from the distant signal to the home 
signal was 3,745 ft. and to the interlocking tower was 4,025 ft. 
In 1901 the average distance from the distant signal to the home 
signal was 1,444 ft. and to the tower was 1,750 ft. 

In addition to signals, derails also form a very necessary part of 
the interlocking equipment at railroad crossings and junctions. 
A derail is a device for throwing an engine or car from the track; 
and the presence of such equipment in the plant is to guarantee 
that the train shall stop before it reaches the crossing should the 
route not be lined up for it to proceed. The derail is generally 
.located about 500 ft. from the crossing, while the home signal is 
placed about 58 ft. in the rear of the derail, as shown in Fig. 16. 
By placing the derail this distance from the crossing there is 
practically no chance for the derailed train to continue on the ties 
and reach the crossing. 

All signals and derails at an interlocked crossing stand nor- 
mally at danger to stop traffic. When they are set against move- 
ment of traffic, they are said to be ''normal;" when they are in 
position for movement of traffic, they are said to be ''reversed." 
The levers corresponding to these positions are also normal and 
reversed. Usually one lever is assigned to operate each function. 



INTERLOCKING 



25 



15. General Order of Locking Signals and Derails. — When a 
movement over a crossing is desired, the towerman first closes 
the two derails on the track, then he clears the home signal on the 
side from which the train is approaching, and finally he clears the 
distant signal on that side. When a derail on one track of a 
crossing is reversed, it locks the derails of the conflicting tracks 
at normal. When the derails are reversed the home signal may 
then be reversed, and this movement locks the derails reversed. 
The distant signal is then unlocked and may be reversed, locking 
the home signal clear or reversed. The levers in the tower must 




Home Signer f 



^S 



' Distanf Signal 



-SOO - - -'■"^■SS- '^ IZOO to 6000- ■ ■ 

5" 



LOCKING SHEET 


mERse 


LOCKS 


mERSl 


LOCKS 


1 


® 


9 


SpareSpace 


2 


(i)@/3 


10 


8.12 


3 


&) 


II 


SpareSpace 


4 


®©/s. 


13 


6.10 


s 


SpareSpace 


13 


<S®2 


6 


8.12 


14. 


© 


7 


SpareSpace 


IS 


(B)(S)4 


8 


6,K) 


16 


@ ■ 




Fig. 16. — Single track crossing a single track. 



be operated in this order, for the construction of the plant will 
permit no other. To put the plant normal the functions must be 
operated in the opposite order. 

To have a train pass from A to 5 in Fig. 16, the towerman 
clears derails 6 and 10. This locks derails 8 and 12 open. He 
then clears the home signal 2, which locks 6 and 10 closed, and 
13 normal. He finally clears distant signal 1, which locks 2 
clear. To set the track to normal again the towerman sets 
distant signal 1 to caution, then home signal 2 to the stop 
position, and finally opens derails 6 and 10. 

In order to line up a route through an interlocking plant, there- 
fore, all the derails on the route must be reversed, locking those 



26 



RAILWAY SIGNALING 



on conflicting routes normal. Clearing the home signal then 
locks all the derails in the route reversed and all opposing direc- 
tion signals normal. Finally, clearing the distant signal locks 
the home signal reversed. 

16. Locking Sheet. — A locking sheet is a tabulated statement 
of the order in which the levers of any particular plant interlock 
one another. In the locking sheet shown in connection with Fig. 
16, the levers in the first column are all understood to be reversed. 
Those in the second column that are reversed are shown as such 
by drawing a circle around them ; otherwise they are understood 
to be normal. The chart reads: 

Lever 1 reversed locks lever 2 reversed; 

Lever 2 reversed locks levers 6 and 10 reversed and 13 normal: 
and so on to the bottom. 

The numbers on the functions correspond to the numbers on 
the levers in the tower; and since interlocking machines are 
built with lever spaces in multiples of four, it is well to distribute 
the extra spaces through the middle of the machine for additional 
levers that may be added later. 



REVERSED 



LOCKS 



® W (7) 



LEVER 


whbn 


LOCKS 


5 


(7) 


® 



Fig. 17.— Form of sheet for special locking. 

If there are levers that operate special locking, the sheet must 
include them also. The usual form of expressing such lock- 
ing is as shown in one of the forms in Fig. 17, which in each 
case reads lever 5 reversed locks 4 reversed when 7 is reversed. 

When facing point locks, designated F.P.L., are used to lock 
the derails and switches, the two locks on the same route at a 
crossing are generally thrown by one lever and the two derails by 
another. In the case of switch and lock movements, designated 
S.L.M., one lever in a mechanical plant is generally assigned to 
each derail or switch, although two may be assigned where power 
is used. 

If facing point locks were used in Fig. 16, the numbering and 
locking would be as shown in Fig. 18. A single track crossing a 
double track where switch and lock movements are used, has a 
locking sheet as shown in Fig. 19. Back-up movements, or 



INTERLOCKING 



27 



those that run counterwise to the normal direction of traffic, are 
governed by dwarf signals. Otherwise the installation is the 




^0-/ 



^JUFPLG 



LOCKING SHEET 



Heyirse 


LOCKS 


mtR5E 


LOCKS 




® 


9 


® 




®/J 


10 


Spare 




® 


II 


7 




Q>is 


IZ 


Spare 




apar^ 


13 


®z 




® 


14 






II 


IS 


® 4 




Spare 


16 


® 




Fig. 18. — Facing point locks. 






SL 


^ 


13 i 19. 


^20 




-^li 


^ 


^ 




— F 


T-> 


~v 


Ik 





LOCKING SHEET 




REVERSE 


LOCKS 


REVERSE 


LOCKS 


1 


® 


II 


Spare 


2 


®@/7 


12 


79,t2JS 


3 




IS 


6JZ 


4 


@@/6 


14 


Spare 


S 


Spare 


IS 


GJ2 


6 


1 9, 13, IS 


16 


Spare 


7 


&JZ 


17 


©®2 


8 


Spare 


18 


@ 


9 


ijZ 


19 


®@I0 


10 


(i,@l9 


20 


® 




Fig. 19. — Single track crossing a double track. 

same as for a single-track crossing. The derails for the dwarf 
signals are generally located about 250 to 300 ft. from the crossing. 



28 



RAILWAY SIGNALING 



17. Diverging Routes. — There are many cases of diverging 
routes that require more than one signal on a post. In some 
instances the diverging routes are high-speed hues and in others 
they are low-speed lines. Where two high-speed lines diverge 




REVERSE 


lOCKS 


REVERSE 


LOCUS 


1 


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7 


BjS 


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8 


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9 


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s 




II 


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6 


7<S 


12 qn 1 



Fig. 20. — High speed diverging routes. 

there is a home signal and sometimes a distant signal for each 
route, although generally there is only one distant signal. Fig- 
ure 20 shows an arrangement for two high-speed diverging routes. 
The upper blade of the two-arm signal governs the superior route, 

4- nZ=, :HA, 



2 -J 



^ 



L0CKING5HEET 



REVERSE 


LOCKS 


I 


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2 


® 


3 


4 


4 




5 


Spare 


6 


(?)P 


7 


3.4 


8 


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Fig. 21. — Single track and turnout. 

which is usually the straight one, while the lower blade governs 
the inferior route, which is generally the diverging one. In the 
Railway Signal Association standard the lower blade stands 22 
ft. 6 in. above the foundation and the upper one 7 ft. higher. 



Trnr 



Fig. 22. — Single track and two low speed diverging routes. 

Whenever a very low-speed route diverges from a main line, 
the high-speed route may be governed by a high signal, while the 
inferior route may be governed by a dwarf signal placed either 
on the lower portion of the high signal post or on the ground at the 



INTERLOCKING 29 

base of the post. Figure 21 shows an arrangement where the 
two blades are on the same post. When the dwarf signal is 
cleared, the high-speed home and distant signals are respectively 
in the stop and caution positions. The inferior or low.-speed 
route may be a cross-over, a transfer, or a spur. The dwarf 



Fig. 23. — Trailing point crossover. 

signal on the siding is to govern trains moving from the siding to 
the main track. 

Where there are two or more inferior routes diverging within 
a comparatively short distance, the common practice is to have a 
set of high signals to govern the main line and a dwarf all of the 




Fig. 24. — Single track crossing and high speed diverging route. 

others. In Fig. 22 the dwarf may govern either of the diverging 
routes. It will show a clear indication when any of the diverging 
routes is lined up. 

As the dwarf signal is low, the engineman can see it only a 
short distance ahead and therefore he is required to reduce his 



30 



RAILWAY^ SIGNALING 



speed and to keep his locomotive under control as he approaches 
the turnout. On the other hand, the blade must be high in the 
case of high-speed routes in order that the engineman may see 
it at a distance. Besides requiring the engineman to check his 
speed, the dwarf signal has two other advantages: (1) that it is 




Fig. 25. — Single track crossing and transfer track. 

much cheaper than the high signal; (2) that it can always be 
placed next to the track it governs, even between tracks if 
necessary. 

Figures 23 to 26 inclusive illustrate additional cases of route 
signaling. 




Fig. 26. — Double track diverging routes. 

18. Movable Bridge Interlocking. — Viewed from the standpoint 
of train movements, the question of horizontal and vertical align- 
ment of the track at each end of the bridge is the most serious 
that comes up in connection with drawbridge operation. The 
bridge when properly closed not only must be so placed that the 
track centers are continuous, but also it must be so seated that 
the top of the rail is continuous. For this purpose end lifts are 
required for horizontal swing bridges to place the rails to the 
proper surface and locks to secure them in this position and also 
in proper alignment. Locks are necessary also for lift bridges in 
order to secure the continuity of the track. 



INTERLOCKING 



31 



The rail ends may be cut either mitered or square. In case of 
mitered joints the full thickness of the web of the rail should 
continue to the end of the point. The point should be placed in 
a trailing position at each end of the bridge on double track and 
in a trailing position towards the center of the bridge on single 
track. Some sort of provision should be made, as for instance 
the addition of an easer rail on the outside of the joints, to support 
the train wheels across the gap between the bridge rails and the 
approach rails. 

Signals are used to protect movable bridges in practically the 
same manner as railway crossings. The interlocking machine is 
frequently placed on the bridge itself. The interlocking should 
be so constructed that the bridge should be locked in aHgnment 
for traffic before the signals can be cleared; and conversely, the 



^J^FPL3 6 -' 




/? 



9FPL.I0 



5- Bridge Couphr 
6- Bridge Lock 
7- Engine Lock 
LOCKING SHEET 



REVERSE 


LOCKS 


REVERSE 


LOCKS 


1 


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7 




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Fig. 27. — Drawbridge interlocking. 



signals should all be locked at the stop position when the bridge 
is open. Where mechanical interlocking is employed the con- 
nections between the pipes on the bridge and those on the roadbed 
are made by means of couplers. The order in which the tower- 
man operates the functions to close a bridge and line up the 
route for trains is: motor, bridge locks, couplers, derails, facing 
point locks, home signal, and distant signal. Each one reversed 
locks all those in front of it reversed. There is, then, no possi- 
bility of opening the bridge until every signal and derail is set at 
the stop indication. In order to open the bridge the levers must 
be placed normal in exactly the reverse order. Figure 27 gives 
a plan of the signal and derail arrangement together with a lock- 
ing sheet for a single-track swing bridge. The derails are placed 
at least 500 ft. from the bridge so that the derailed trains cannot 



32 RAILWAY SIGNALING 

run into the stream. Usually each derail and facing point lock 
has its own lever to guarantee safety in operation. In the case of 
double-track Hnes the derails for back-up movements should be 
not less than 300 ft. from the bridge. 



^ ^ 11 U II 

Fig. 28. — Drawbridge interlocking. 

19. Requirements for the protection of traffic at movable 
bridges as defined in the Proceedings of the Railway Signal 
Association in 1916: 

The protective appliances at drawbridges consist in devices for insur- 
ing that the bridge is in proper position, and the track in condition for 
the passage of trains over draw, or for reduction to a minimum of the 
damage in case of trains not stopping when track is not in condition 
for passage of same over draw; also the usual devices for protection 
against damage in case of derailment. 

The protective devices may be classified under the headings: 

(a) Interlocking power and bridge devices. 

(6) Bridge surfacing, aligning and fastening devices. 

(c) Rail-end connections. 

{d) Signaling and interlocking. 

(e) Guard rails. 

(a) Interlocking Power and Bridge Devices. — Interlocking the draw- 
bridge devices so that their movements must follow in a predetermined 
order to protect the drawbridge machinery. 

(b) Bridge Surfacing, Aligning arid Fastening Devices. — Drawbridges 
should be equipped with proper mechanism to surface and align them 
accurately and fasten them securely in position. This condition can 
be secured by the use of efficient end hfts in case of swing bridges, and 
by proper end locks in case of lift bridges. 

(c) Rail-end Connections. — Rail ends may be mitered or cut square. 
Mitered rails where lapped should retain the full thickness of the web 
to the points. The points should be trailing to normal traffic where 
possible; on single-track bridges the points should be trailing to traffic 
entering the movable span. 

Where rail ends are cut square or mitered and not lapped, they should 
be connected by shding sleeve or joint bar or by easer rails to carry the 
wheels over the opening between the end of bridp;e and approach rails. 



INTERLOCKING 



33 



{d) Signaling and Interlocking. — If trains are to proceed over draw- 
bridges which are in service, without first stopping, interlocking should 
be installed which will provide that the drawspan, tracks and switches 
within the limits of the plant are locked in the proper position. 

This will require: 

1. Locking drawbridge devices. 

2. Locking providing for the proper order of operation of signaling 
devices, such as signals, switches and derails. 

This interlocking will require the following order of operation: 



Before Opening a Drawbridge 



Before Operating Trains over 
Drawbridge 



L Display stop signals. 

2. Unlock rail and bridge devices. 



1. Lock bridge and rail devices. 

2. Display clear signals. 



Since there are various types and designs of drawbridges and various 
drawbridge devices for each of the types, and also various designs and 
types of signahng devices, as well as various locations, from which they 
all may be interlocked and operated, a typical example only of the detail 
order of operations is given; viz., a swingbridge with all its devices 
operated from one location on the drawspan, having home and distant 
signals, derails, etc. 



To Open Drawbridge 

1. Display stop signals. 

2. Unlock derails. 

3. Open derails. 

4. Uncouple interlocking connec- 

tions. 



5. Unlock rail-end connections. 

6. Unlock bridge surfacing, aligning 

and fastening devices. 

7. Operate power-controlling de- 

vice to position permitting ap- 
plication of power to bridge 
machinery. 

8. Withdraw rail-end connections. 

9. Withdraw bridge surfacing, 

aligning and fastening devices. 
10. Open bridge. 



To Pass Trains Over Drawbridge 



1. Close bridge. 

2. Insert bridge surfacing, aligning 

and fastening devices. 

3. Insert rail-end connections. 

4. Operate power-controlling device 

to position preventing applica- 
tion of power to bridge ma- 
chinery. 

5. Lock bridge surfacing, aligning 

and fastening devices. 

6. Lock rail-end connections. 

7. Couple interlocking connections. 



8. Close derails. 

9. Lock derails. 

10. Display clear signals. 



34 



RAILWAY SIGNALING 



Derails. — The above example of order of operation includes derailing 
switches, but their use is not recommended in all cases. Each situation 
must be given special study with respect to (a) the use of derails, smash 



1. 4li-i^- 

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boards or similar devices; (6) their location with respect to drawspan; 
and (c) the use and length of guard rails. 

(e) Guard Rails. — Guard rails should be provided as for fixed bridges, 
except for the necessary breaks at the ends of the movable span. Ob- 



INTERLOCKING 35 

struction to derailed wheels which are guided by the guard rails should 
be reduced to a minimum. 

(/) Rail Attachments. — The rails and attachments should be separated 
from the metallic structure so track circuits may be successfully operated 
the entire length of the bridge. 

{g) Bridge Devices. — The various bridge devices should be so designed 
.that Railway Signal Association interlocking apparatus may be used. 

{h) Locking. — Electric and time locking are regarded as adjuncts. 

20. Track Diagram and Manipulation Chart. — ^A track dia- 
gram and a manipulation chart are usually placed in each tower 
for the benefit of the signalmen. The track diagram is a plan of 
the track layout showing the relative positions of the switches, 
derails, and signals with the number assigned to each that 
corresponds to the lever that operates it; the manipulation chart 
shows the order in which these functions must be operated to 
line up a certain route. The diagram and chart are made on 
rather a large scale and are hung on the front wall of the tower so 
that the signalmen can see them as they stand to manipulate 
the levers. A typical track diagram and manipulation chart 
are illustrated in Fig. 29. 



CHAPTER IV 
MECHANICAL INTERLOCKING 

INTERLOCKING MACHINES 

21. General. — Two kinds of interlocking plants are built — 
mechanical and power. In the mechanical plant, the levers are 
operated by hand; and the movements are transmitted by hand 
power to the switches, signals, and derails by means of pipes, 
wires and other mechanical appliances. In the other type the 
levers are operated by hand, but they are so constructed as to 
bring into" action some kind of power to operate the switches, 
signals, and derails. The power most commonly used is air or 
electricity, or a combination of the two; and such plants are 
known as pneumatic, electric, or electro-pneumatic. 

The levers of an interlocking plant are arranged in a row across, 
the second floor of an interlocking tower parallel to one set of 
tracks in the plan. The front of the interlocking machine is the 
side on which the towerman stands while he operates the levers. 
The levers are numbered from the left to the right of the tower- 
man as he stands in position to operate his machine. The 
location of the levers in the machine should correspond somewhat 
to the respective locations of the functions on the ground. In 
the case of the railroad crossing, those signal levers that stand 
nearest together on the ground should be grouped nearest 
together in the machine. Usually the signal levers are on the 
ends and the switches and derails between. The arrangement 
of the levers should be such as to cause the signalman to walk 
back and forth as little as possible to manipulate them. 

The mechanical machines may have either horizontal or 
vertical locking. The horizontal type is known as Saxby and 
Farmer; the vertical has three similar designs. Standard or Style 
A, Johnson, and National. Most of the vertical locking plants 
in use have Style A machines. 

22. Horizontal Locking. — Figure 30 illustrates an eight-lever 
Saxby and Farmer interlocking machine, while Fig. 31 shows it 
more in detail. The figures used in the explanation of the system 

36 



MECHANICAL INTERLOCKING 



37 



j 

f 


1 



Fig. 30. — Saxby and Farmer interlocking machine. 




I !! I !! I 
LJU4-JU 



H 



111 !i 



EHrnjkl 



^ — ^i 



Fig. 31. — Saxby and Farmer interlocking machine. 



38 



RAILWAY SIGNALING 



of horizontal locking refer to the sketch in Fig. 32. Lever 1 
is pivoted near its lower end at 3 and is shown in the sketch in 
its normal position. Rocker-link 5 is pivoted at its center 4. 
The back end of this rocker-link is connected by means of the 
universal link 6 to the locking shaft crank 7, which in turn is 
rigidly fastened to the locking shaft 9. Horizontal locking bar 
10a is connected to locking shaft 9 by means of the locking bar 
driver 8. As the towerman pulls on latch 2 of lever 1, he lifts for 




Fig. 32. — Saxby and Farmer locking. 

one-half its throw, the back end of rocker-link 5. This movement 
is transmitted to bar 10a which is thus driven half its throw. 
The dog riveted on top of bar 10a makes miter contact with cross- 
lock 11, and the half throw of bar 10a gives full throw to 11, 
making contact with the dog on the other horizontal locking bar 
106 and locking it in its normal position. 

The lever is then thrown over to the opposite end of the rocker- 
link as shown in Fig. 33; and as the latch is released and comes 
into proper position, it imparts the other half of the movement to 
the horizontal locking bar. While the movements of the signals 



MECHANICAL INTERLOCKING 



39 



and switches are made by the lever, the movements of the locking 
are all made by the latch. This is known as preliminary or latch 
locking, and is very fundamental in the construction and opera- 
tion of the machine. This insures that not only must the lever be 
placed in its full normal or reverse position, but that it also 
must be locked in this position before any other levers can be 
unlocked. Furthermore, with this arrangement the signalman 
can apply only a comparatively small 
amount of pressure against the lock- 
ing bed; whereas, if the lever, itself, 
were connected directly to the lock- 
ing he might be able to apply enough 
force to cause the locldng to break 
or fail. 

The locking shafts, locking bars, 
dogs, cross-locks, and brackets 
assembled in working order con- 
stitute what is called the locking 
bed. The locking bars are J-^ by % 
in. in section and are arranged in 
pairs. The pairs have % in. clear 
space between them. Most of the 
machines are constructed with half 
as many brackets as levers and they 
are spaced to come between the lock- 
ing shafts and not directly above 
them. The cross-locks may extend 
between two locking bars or entirely 
across the bed depending upon the 

particular locking construction. The cross-locks are % in. 
square in section and have a throw of % in. When the lever is 
normal, the locking bar stands as far to the right as it is possible 
to go; when the lever is reversed, the bar stands as far to the left 
as it is possible to go, moving from one position to another 
through a distance of 1% in. 

23. Special Locking. — Special locking is applied to the Saxby 
and Farmer machine by having a long crooked dog fastened to the 
locking bar in such a manner as to permit it to swing about one 
end. This is called a swing dog or ''when" dog. The cross-lock 
is made in two pieces, one on each side of the swing dog. The dog 
on one locking bar will drive the cross-lock to engage another 




Fig. 33. — Saxby and Farmer 
interlocking machine. 



1 1 


) |o o o /~ 


— » \ 


' ^. 




1 ^,=,-^ 4 \ \ 


1 CO^ 


— ^ 1 


. k 




) |o o o \, 


— >^ 


1 I 



40 RAILWAY SIGNALING 

when the swing dog is in place between the two sections of the 
cross-lock. That is, dog 1 reversed will lock 2 normal when 
swing dog 4 is reversed. When 4 is reversed it makes the cross- 
lock practically continuous, for 4 can swing about its pivot P, 
Fig. 34. If 4 is not reversed, reversing 1 will have no effect on 2. 
Figure 35 shows the different forms of dogs used in the Saxby and 

Farmer machines. Numbers 
1 to 13 inclusive are locking 
dogs; 14, 16, and 18 are left- 
hand swing dogs; 15, 17, and 

19 are right-hand swing dogs; 

20 is a swing dog trunnion; 

Fig. 34.-Special horizontal locking. 2I is a locking bar driver; 

32, 33, and 34 are stock pieces for making locking bars and 
cross-locks. 

24. Vertical Locking. — In the case of machines with the vertical 
type of locking, the locking bed stands vertically; whence the 
name, vertical locking. The levers are substantially the same as 
in the Saxby and Farmer machines and they operate rocker-links 
in practically the same manner, but the remainder of the con- 
struction is very different. Figure 36 shows a view of the Style A 
machine, while Fig. 37 gives more details of the construction. 
The end of the rocker-link is connected by a link to a tappet 
bar, which it sHdes up and down through a distance of l}/ie in. 
On the sides of the tappet are V-shaped notches and on the front 
are tappet pieces that engage dogs fastened to small locking bars 
which sHde horizontally through locking guides. Two or more 
dogs are fastened to each bar, and as the tappet is pushed or 
pulled it impinges the dog by miter contact. If the bar is free to 
move, the lever may be thrown. The sliding of the bar will cause 
one or more dogs on it to engage the notches of other tappets, 
locking them in either the normal or reverse position. The lock- 
ing bars are % in. in section and have a throw of ^6 in. Lifting 
the latch in the vertical machine gives the rocker-link and the 
tappet one-half their throw, and releasing it at the other end of 
the quadrant completes the locking. 

Vertical machines are ordinarily built with not more than 
four locking plates, which are numbered from the top down, 1, 2, 
3, and 4. The plates are made to contain both back and front 
locking bars. Three bars may be placed side by side in the back 
of each locking plate and five in front, giving a maximum of eight 



MECHANICAL INTERLOCKING 



41 



bars to each plate. The back locking dogs operate in the same 
plane as the tappet bars. If it should become necessary at any 
time to install more locking bars, additional locking plates may be 



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24 

METHOD OF SPLICING BARS 



32 



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33 



niy 



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34 



Fig. 35. — Locking details of Saxby and Farmer interlocking machine. 



provided by using extension legs for the machine. In making 
up a dog chart, the back locking for each space is shown above 



42 



RAILWAY SIGNALING 



the front locking of that space. Figure 38 illustrates an example 
of back locking. 1 and 2 are tappet bars so arranged that 1 re- 
versed locks 2 normal. 

25. Special Locking. — The swing dog in the vertical locking 
machine is constructed somewhat differently from that in the 
Saxby and Farmer machine. The dog is fastened to tappet 4 in 




Fig. 36. — Style A interlocking machine. 



Fig. 39 and swings in a vertical plane between the adjacent dogs a 
and b. The special locking is in the plane of the front locking 
bars. In the figure, 5 reversed locks 1 and 2 normal when 4 is 
reversed. If 4 is not reversed, however, reversing 5 has no 
effect on 1 and 2. 

In Fig. 40, the numbers 1 to 36 inclusive represent front 
locking dogs; 37 to 39 are front couplings; 40 to 42 are front 
carriers; 43 is a special swing dog; 44 to 49 are tappet pieces; 



MECHANICAL INTERLOCKING 



43 







I I, I LOCKING BAR 

Fig. 37. — Style A interlocking machine. 



ij ii T 



1 



s^^Sp. 



Fig. 38.— Back locking. 



l^^i . r'<®^ 



Fig. 39. — Special vertical locking. 






44 



RAILWAY SIGNALING 



50 to 65 are back locking dogs; 66 and 67 are back couplings; 
68 to 71 are back carriers; 72 to 77 are front locking dogs; and 
83 is a short piece of steel locking bar. 



11 



loooof 

ia 



18 3 4 5 

6 7 8 9 10 

D D E> B B D ^ 

13 14 15 16 17 18 19 

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78 79 80 81 8S 83 

Fig. 40. — Locking details of style A interlocking machine. 

26. The Dog Chart. — The dog chart is a plan showing the lock- 
ing arrangement of any particular interlocking machine. The 
dog chart for the Saxby and Farmer machine is made up with the 



MECHANICAL INTERLOCKING 



45 



33 






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RAILWAY SIGNALING 



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MECHANICAL INTERLOCKING 



47 



front of the locking bed at the top just as an observer would see 
it if he were standing at the back of the machine and facing the 
operator in position to manipulate the levers. This throws 
lever 1 to the right-hand side on the drawing, as shown in Fig. 41. 
The figures across the top represent numbers of the levers, while 
those on the side refer to the locking bars. The circles represent 
the points where the locking shafts connect to the locking bars. 
On the dog chart for the Style A machine, illustrated in the 
same figure, the back locking is shown above the front locking. 




y 




kv>!r' 




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i 



Fig. 44. — The Johnson interlocking 
machine. 



Fig. 43. — The National interlock- 
ing machine. 

„ j^ 1 are back and front locking spaces of the first or top plate; 

H 1 

„ j^ 2 are back and front locking spaces of the second locking 

plate; and so on to ^ j- 4. The position of lever 1 is at the left 

^ J 
on the sheet. 

Figure 42 shows dog charts for Saxby and Farmer and Style A 
machines to operate a trailing point crossover between double- 
track lines. 

Figure 43 represents a National interlocking machine while 
Fig. 44 represents a Johnson, 



48 



RAILWAY SIGNALING 



The vertical locking plant requires less room than the hori- 
zontal, but has more wear between the dogs and the notches in the 
tappets. In the case of the vertical locking plant the locking is 
below the floor, while in the case of the horizontal locking, it is 
above the floor. Lying below the floor, often in a dark room, the 
vertical locking frequently does not get the attention and care it 
should have. 




Fig. 45. — The Stevens interlocking machine. 

27. Stevens Interlocking Machine. — A dwarf type of inter- 
locking machine constructed with lever instead of latch locking is 
known as the Stevens. It operates with a vertical type of locking 
placed in a horizontal bed, but the stroke of the tappet is much 
longer than is the case with the Style A machine. It is used 
principally where a number of yard switches can be controlled 
from a central point or where it is desired to install some form of 
temporary interlocking. 



CHAPTER V 

MECHANICAL INTERLOCKING 

OTHER EQUIPMENT 

28. Leadouts. — The equipment that transfers the motion from 
the levers in the tower to the horizontal pipes and wires on the 
ground is called the leadout. It includes all of the vertical pipes 
and wires within the tower and all the rocking shafts, cranks, and 




Fig. 46. — Rocking shafts for leadouts. 



deflecting bars in the case of pipes, and wheels and chains in the 
case of wires that connect the pipes and wires inside with those 
outside the building. In the case of the rocking shaft, shown in 
Fig. 46, the vertical pipe connects 
with the outside arm and the hori- 
zontal pipe with the adjustable 
inside arm. The shaft itself may be 
either square or hexagonal, as the 
figure illustrates, the square ones 
being most commonly found in 
practice. 

Figure 47 represents a vertical crank and Fig. 48 a horizontal 
and a vertical deflecting bar. The horizontal crank is illustrated 
4 49 




Fig. 47. — R. S. A. vertical crank. 



50 



RAILWAY SIGNALING 




in Fig. 60. In the case of the deflecting bar, the curved bar 
sHdes between two sets of rollers supported by the frame. Figure 
49 shows the use of both rocking shafts and deflecting bars in a 
leadout. 

29. Pipes and Couplings. — The 
movements of the levers in a 
mechanical plant are transmitted 
to the derails, home signals, and 
switches by means of 1-in. iron 
pipes, and to distant signals by 
means of No. 8 or 9 steel wire. 
Home signals and dwarf signals 
are sometimes operated by wires. 
The ends of the pipes are fastened 
together by means of couplings 
over the outside and 23'^2-in. steel 
plugs 10 in. long on the inside, as 
illustrated in Fig. 50. Two M-in. 
rivets pass through each plug at 
the end of each pipe. The pipe 
is fastened to a crank by means of 
a steel rod with a tang on one end 

Fig. 48.— Horizontal and vertical and a Solid Or SCrew jaW On the 

deflecting bars. other, a number of different forms 

of which are shown in Fig. 51. 

30. Stuffing Box. — It very often becomes necessary to carry 
pipe lines under a street, in which case the pipes are placed inside 
of larger pipes enclosed at the ends by stuffing boxes, as illustrated 
in Fig. 52. The outer pipes are filled with oil to preserve the 
materials and to eliminate the friction. 

31. Pipe Carriers. — Pipes are supported on pipe carriers placed, 
as a rule, 7 ft. apart on straight lines and 6 ft. apart on curves. 
This length of space prevents buckling when the pipe is in com- 
pression. The distance center to center of levers in a mechanical 
plant is 5 in., while the distance center to center of pipes as they 
are placed in the carriers is 2% in. The two rollers in the carrier, 
the one below and the other above the pipe, tend to reduce the 
amount of friction during the movement of the pipe line. Where 
there is only one set of rollers in the frame it is called a one-way 
carrier; where there are two, a two-way carrier; and so on. 
The pipe carrier is fastened to its foundation by means of a pipe 




MECHANICAL INTERLOCKING 



51 



carrier base. The transverse carriers, represented by Fig. 54, 
rest on two track ties and carry the pipes under the rails at 
right angles to the track. 




6y J^/'^rrif/ ^r/,:^ 









CL^ 




TOWER LEADOUTS 

(MOUNTED DEFLECTING BARS AND ROCKING SHAFTS) 



IJWJ^IZ 



RSA 
1206 



Fig. 49. — R. S. A. tower leadout. 



32. Compensators. — Compensators are inserted at the proper 
places in pipe and wire hnes to provide automatically for changes 
in length, due to expansion or contraction caused by differences 



52 



RAILWAY SIGNALING 



Sfandarc^ I Signal Pi'pe^ 



^% 



f "''8-A [^'•^/"• •^ 4 of Pipe ifireM ll^fhds.perinch 



PIPEJOIMTCOMPLETE 
------„ 10"-- 



■\ 



TTT 



■2 -- 



^ 



-/'--> 



^it 



Jk-^i 



^0.2S6 Prill-' 



J^--//f---H 



/^Z6/5 



(tierciiank hanronorsted) 



(t 



i^© 



Soft Iron RIVET 



"irii?,ii'j'[i'^'iTi;iiTiT.fT 



ii'diU'i!i!iiiiili'ilLii'l! 




CCd//'Z///(5 
Fig. 50. — R. S, A. 1-in. pipe and coupling. 



C3=3 



JHE 



iLJ-i 



Sr 



■XT^^^izi 



~[w" 



Jl3=:3 



^^ 



^I 



XB^=3 




Fig. 51. — Solid and screw jaws. 



I — 2"PlfE 






k-^:^^;:.:^ 



^ 1 


■■;;?:-■. 


=T-^. 






h 


IliiM^^^^^^^^^^ 



Fig. 52. — R. S. A. standard stuffing box. 



MECHANICAL INTERLOCKING 



53 



in temperature. In the case of a pipe line, the compensator 
reverses the direction of motion so that the change in length on 




Fig. 53. — Pipe carrier. Universal base. 

one side of it will just offset the change on the other side. Where a 
line is straight and one compensator is used, it should be in the 
middle. If two are used, they should be 
located at the quarter points. The com- 
pensator used in straight pipe line con- 
struction is called a ''lazy jack." It is 
made of two angles, 60 and 120 degrees, 
with a link connecting them, as shown in Fig. 55. One 



Fig. 54.— R. S. A. 
two-way transverse 
pipe carrier. 




Fig. 55. — R. S. A. "lazy jack" pipe compensator. 

compensator is used for a pipe 50 to 650 ft. long and two for a 
line between 650 and 1,300 ft. In the case of a 90-degree change 



54 



RAILWAY SIGNALING 




in the direction of a line, a crank if properly placed may be used 
as a compensator. Figure 56 illustrates a straight arm com- 
pensator. 

The following example will serve to illustrate 
the principle of applying compensation to a pipe 
line: A pipe as a part of an interlocking plant is 
used to throw switches 1 and 2 of a main-line 
crossover. The switches are normally Hned up 
Fig. 56.— r. s. for the main tracks clear. The dimensions of the 
A. straight arm track layout are given in the sketch, Fig. 57. 

compensator. mi • t> i ' o 

The motion from the leadout is a push, which 
causes a pull beyond the first compensator. Since the motion to 
be given to the switch 1 is a push, the angle crank at A should be 
a compensator. The direction of motion beyond the second com- 
pensator is a push; and since the motion to be given switch 
2 is a pull, the crank at B should also be a compensator. 
The calculated locations of the "lazy jacks" are shown in the 
figure. 

Should a compensator figure to come where a pipe carrier is 
located, the compensator should be placed at the middle of the 
adjoining span. 






29 



.1- 






190 



-I09.5j 
-BOS - 



><-/S'-> 



f5'\ 



-^ ^B 



Fig. 57. — Compensation. 



The following table. Fig. 58, shows the lengths and positions 
of crank arms recommended by the Railway Signal Association 
for compensation. 

A type of wire compensator is shown in Fig. 59. It operates 
by means of the lever at the base of the post and is so arranged 
that the tension on the two wires will be constant. On one arm 
of the lever are two chain wheels and on the other is a rather 
heavy counterweight. When the wires shorten, the counterweight 
rises; when they lengthen, the counterweight drops, adjusting 
the length automatically. 



MECHANICAL INTERLOCKING 



55 



33. Field construction of pipe lines as recommended by Com- 
mittee II of the Railway Signal Association in Volume XIV, 



1917, of the Proceedings:^ 





< U 


--> 


L >ir ^^ ^ 








( 

Val(/6 
ofe 
oflh 

Value 
lines 
used! 
unect 


A^22" 

^sof't 

X pan St 
neofnc 

^s ofsp 
cornper 
h corn PL 
jcxl len 


B 

\ X- 


X l3"Upt0700', 
- ^ 18" » ^>I200 

76edonO.Odofan 
an increase of 10 
earestf-^"isgiv 

"U "for^ivina ferfij. 
irnol fable o feauiva) 
gpipe lines when cr 


"" L 




A 
<— 

'on for 
ifhen 

acing 
isafedc 
onsafin 

crth&. 


inchascafffcfeni 
"f. for each wo' 
en. 

i.and hngfh of 
enf kngfhs to be 
einkc^rms are of 


Temp 
F. 


Lenc^hs o-F Lines Compensafed in Feef J| 


100' 


zoo' 


300' 


400' 


soo' 


600' \ 700' 


sc:a'\90(;'\mo^ 


IIOO< 


110^ 


21 y 


21" 


20i' 


20" 


l$j," 


19" 


idk'; 


18^ 


>7-r 


IT'- 


'6?.\ 


90 


fitr 


21^'' 


21" 


2or 


20 f 


20" 


'S," 


< 


i3"i8r 


">C 


70^ 


2ihr 


21 i" 


2ir 


21 1" 


2li" 


21" 


zor 


20,1' 


20^' mf 


2ok 


SO^ 


Mean Tempera fare U -22^ \\ 


30^ 


^W 


22^ 


Z2r'22'd' 


Z3"23P^Z3f; 


< 


'€ 


H 


10^ 


^w 


Z3" 


23^] 


n: 


p'f^r 


^r 


< 


< 


2sr 


0' 


^2r2Z'i 


I3i" 


23f" 


24Tg 


W."24'4' 


zsr 


isri 


4' 


!4: 


-10 


ZZi" Z3" 


23i" 


Z4" 


H' 


2S" ZSi" 


ze" 


2(i- ZT 


^yi' 


"A" 

Lenqfh 

mft. 


Equivalent for "A "for various lengths of "3 " || 


d'-T' 


6-7^' 


B-'8" 


B^8i" 


B-9" 


B-sr 


B-IO'^ 










?S 


4Z 


39 


37 


3S 


33 


31 


Z9 










SO 


8^ 


7d 


73 


09 


6S 


62 


S9 










7S 


126 


111 


I/O 


104 


98 


93 


88 










100 


168 


IS7 


147 


130 


130 


124 


/I7 










ISO 


2S2 


Z3S 


220 


207 


196 


m 


17$ 










ZOO 


330 


3/3 


294 


270 


261 


247 


235 










2S0 


4/9 


391 


357 


345 


32S 


309 


294 










300 


S03 


470 


441 


4 IS 


391 


37/ 


3SZ 


































note: Since fhemean femp. varies^ if must he fa ken 
for fhelafifucfe where fhe \^ork is ^one. 



Fig. 58. — R. S. A. compensation table. 

1. When lajdng out a pipe line, the selection of a place as free as 
possible from fixed obstructions, such as buildings, bridge girders, abut- 
ments, etc., should be given first consideration. The ahgnment of the 
pipe line should be straight when practicable. Often by slightly chang- 
ing the distance the pipe line is located from the rail, some fixed obstruc- 
tion can be avoided and the line kept straight. Where the pipe Hne 

1 Page 395. 



56 



RAILWAY SIGNALING 



follows a turnout, the curve in the pipe Une should be gradual instead of 
following the rather sharp curve of the turnout, and the maximum 
curvature should not exceed (10) degrees. 

2. Where the interlocking station building is set back far enough from 
the tracks so that an additional track may be laid in front of the building 
at some future time, the pipe line should be installed the standard dis- 
tance from the proposed track, unless extraordinary expense would be 

incurred, rather than install the 
line near the present track and 
later move it when the proposed 
track is laid. 

3. In case the pipe Hne is to be 
run on a bank, sufficient space 
should be provided to strongly 
brace the foundations. In case 
the hne is to be run in a ditch, 
proper drainage should be pro- 
vided; also the slopes of banks 
should be graded or a wall con- 
structed to prevent earth shding. 
Pipe hues should not be run 
under station platforms where it 
can be avoided. 

4. Where necessary to run pipe 
lines under ground, as at road 
crossings, platforms, water tubs, 
stand pipes, etc., it is recom- 
mended that where proper drain- 
age can be provided concrete 
side walls with plank covering 
be used around the pipe line; at 
points where proper drainage 
cannot be provided each pipe 

should be run in a larger pipe with oil and provided with a stuffing 
box on each end. 

5. Stakes showing the final elevation of the rail should be accurately 
driven every fifty feet, then by using intermediate stakes a fine should 
be stretched from which the foundations should be set. 

6. The location of crank and bolt-lock foundations should be determined 
upon first in order that pipe carrier foundations can be so spaced as not 
to interefere with cranks and bolt-locks. Piles should be driven for 
supporting crank, compensator and bolt-lock foundations (and pipe 
carrier foundations if necessary) where the ground is swampy or marshy. 
Everything should be done to have the support for all pipe line apparatus 
as solid as possible and sufficiently braced to prevent shifting. 




Fig. 59. — Wire compensator. 



MECHANICAL INTERLOCKING 



57 



7. In providing compensation for pipe lines the mean temperature of 
the interlocking location should be known; in most cases, it will be the 
same as at the nearest city and can be obtained from the Weather 
Bureau. R. S. A. Drawing 1102, Compensation Table, must be used 
when cutting in pipe lines. 

8. Crosspipes should not be installed until all ties supporting pipe 
carriers are properly spaced and tamped and all tracks are brought to 
the final elevation and Hne, which should be the same for all tracks in 
the interlocking limits. 

9. Crank and compensator foundations should be set to template so 
that with the crank and compensator arms both normal and reversed 
the center of the hole in the arm will coincide with the center of the pipe 
line. Rough forms should be used for the bottoms of foundations 
where necessary; but finished knock-down forms should be used for the 
top portions of the foundations. Where foundations are Hkely to be 
disturbed by frost, cinders should be placed in the bottom of the founda- 
tion hole as well as around the sides, the rough forms being made of 
uniform slope and left in the ground. 

10. Concrete for foundations should be mixed at a central point where 
practicable, from which it can be distributed to foundation locations by 
track barrows or doUies, or mixed on a flat car which can be pushed from 
one point to another. 

34. Horizontal Cranks and Radial Arms. — An abrupt change 
in the horizontal direction of a pipe line may be made by means 






Fig. 60. — R. S. A. one-, two-, and three-way cranks. 

of an angle crank, deflecting bar, or radial arm. The most com- 
monly used of these is the angle crank, which may be one-way, 
two-way, or three-way, as shown in Fig. 60. The angle between 
the arms is usually 90 degrees, although other angles both smaller 
and larger are occasionally used. Figure 61 represents an acute 
angle crank. A three-arm crank, illustrated in Fig. 62, is used 
extensively in connection with switch arrangements. The radial 
arm, shown in Fig. 63, is convenient for changing directions 



58 



RAILWAY SIGNALING 



where the angle is comparatively small. A horizontal deflecting 
bar is shown in Fig. 48. Where the change in direction is gradual, 





fii 



Fig. 61. — R. 
S. A. acute angle 
crank. 



Fig. 62. — R. 
S. A. three-arm 
crank. 



Fig. 63.— R. S. 
A. radial arm. 



as when following an easy curve in the track, the pipes may be 
sprung into place. 



f^ 



^F^ 




5HP 



Fig. ''64a. — Foundations for cranks, wheels, and compensators. 

35. Crank, Wheel, Compensator, and Pipe Carrier Founda- 
tions. — Figure 64a represents designs of concrete foundations 



la- 



o i 



i HOLE 



Fig. 646. — R. S. A. pipe carrier foundation. 

for cranks, wheels, and compensators. Figure 646 illustrates 
a design of a foundation for a pipe carrier. The foundations 



MECHANICAL INTERLOCKING 



59 



should be large enough to eliminate any possibility of their 
shifting due to the movement of the pipes. 

36. Facing Point Lock. — To insure that a switch or point derail 
is properly closed and held in that position, some kind of locking 
equipment becomes necessary. Two devices have been used 
for the purpose, facing point locks, and switch and lock move- 
ments. In the case of facing point locks, two levers are neces- 
sary, one to throw the switch or derail and the other to lock it. 
Switches are locked in both open and closed positions. To 
throw the switch, the plunger is pulled back far enough to clear 
the lock rod, one end of which is fastened to the point of the 
switch and the other is flattened and passes through the facing 




Fig. 65. — Facing point lock. 



point lock casting. After the switch is thrown and is in the 
proper position, the plunger is pushed back through a second 
hole in the lock rod, holding the switch points firmly and prevent- 
ing them from springing open while a train is passing over. The 
plunger of a facing point lock should not be placed between the 
rails, nor at any point where a dragging brakebeam can strike it 
and bend it over or tear it out. Figure 65 illustrates a facing 
point lock. 

37. Switch and Lock Movement. — The switch and lock 
movement, a mechanism so constructed as to throw the switch 
and lock it all with one lever movement, is shown in Fig. 66. In 
the figure the pipe from the lever is connected to the slide bar 
14-15. Another bar runs from escapement crank 20 to the switch 
or derail point. Between upper slide bar 12 and lower slide 
bar 13 is a -roller, 21. As the slide bar is pushed or pulled, the 



60 



RAILWAY SIGNALING 



roller engages the escapement crank, causing arm 20 to move, 
shifting the switch or derail. There is a short plunger that 
passes through a hole in the lock rod as in the case of the facing 
point lock. The first part of the throw of the lever unlocks the 
switch or derail and throws the detector bar described in the 
following paragraph; the second part throws the switch or derail; 
and the third part locks it in its new position. 




//' 7' ZZ' Z/' 

Fig. 66. — Switch and lock movement. 



38. Detector Bar. — A detector bar is a device so constructed 
and operated as to prevent towermen from throwing a switch or 
derail under a moving train. It is a flat bar of steel % to 3^^ in. 
thick, 23^^ in. high, and 53 ft. long, placed along the side of the 
rail and held in position by clips. The bar is connected to the 
same pipe that throws the plunger of the facing point lock or 
that operates the switch and lock movement. As these functions 
are thrown, the detector bar must travel horizontally parallel 
to the rail. It is so constructed that while it moves horizontally 
it must also move vertically, rising as it moves an inch or more 
above the top of the rail. If a train should be standing or moving 
on the rail, any attempt to throw the switch or derail would 
fail when the detector bar rises against the tread of the wheel. 
Four different types of detector bars are shown in Fig. 67. 

39. Bolt Lock. — The bolt lock is an appliance to guarantee that 
the home signal cannot be placed in the proceed position until 
the derail or switch is cleared. In addition to the throw rod and 
lock rod, another rod or bar is sometimes connected to the 
switch point or derail. This bar extends out to cross the pipe 



MECHANICAL INTERLOCKING 



61 



or wire line that operates the home signal. In the pipe line at 
this particular point is inserted a flat bar. Each of these bars 
crossing at right angles has a notch so placed as to preclude a 
certain order of switch and signal movement. If for any reason 




the switch should fail to be moved, even though its signal lever 
had been thrown, the home signal could not be operated. Figure 
68 shows a one-way bolt lock. All of these additional precautions 
and safety devices are installed to guarantee against any possi- 
bility of failure on the part of pipes or other ground equipment. 



62 



RAILWAY SIGNALING 



40. Head Rod and Switch Adjustment. — The two switch 

points are connected near the end by a head rod shown in Fig. 72. 
If track circuits are installed for any purpose, it becomes neces- 




FiG. 68. — One-way bolt lock. 

sary to insulate the two rails to avoid a short-circuit. To ac- 
complish this, some kind of fiber is generally used for insulation. 
To this head rod is fastened one end of the throw rod that 



•qiP 



iilil 



, ri" "i'l'S^ "^ iliiiiC 


:^m- 


^^^^ 






— '.^j. 



Fig. 69. — R. S. A. insulated rods. 



operates the switch. There is an adjusting arrangement where 
the throw rod connects to the head rod whereby the former 
moves a certain distance before it begins to throw the switch. 



Fig. 70. — Switch adjustment. 

This is done to offset a part of the difference in travel between 
the lever throw and the switch movement. The remainder of 
the difference is taken up by using unequal lengths of crank 
arms, 



II 



MECHANICAL INTERLOCKING 



63 



41. Lock Rod. — An insulated front rod and a lock rod used in 
connection with facing point locks and switch and lock move- 
ments is shown in Fig. 71. Figure 72 represents a switch locked 



ENLARGED VIEW OF INSULATION 



IF 



^=^^ 



1^^ 



Fig. 71. — Insulated front and lock rods. 

by a facing point lock after it is thrown by a separate lever, and 
Fig. 73 represents a switch operated by a switch and lock move- 
ment. In both cases the detector bar and bolt lock attachment 




LJ LJ l_J U U- 
Fig. 72. — Facing point lock and bolt lock applied to a switch. 

are added. The detector bar stands in front of the switch points. 
Figure 74 shows the layout for a double slip switch with movable 
point frogs. One lever operates by means of a three-way crank 




TIQ fluuuuuuuu'uuu 

Fig. 73. — Switch and lock movement and bolt lock applied to a switch. 

and a rocker shaft one facing point lock for each pair of slip 
switches. 



64 



RAILWAY SIGNALING 




MECHANICAL INTERLOCKING 



65 



42. Derails. — There are three types of derails used in connec- 
tion with interlocking plants. The oldest is the split point, shown 
in Fig. 75. As this has one rail broken it has the disadvant- 
age of making the track somewhat unsafe, and therefore is used 
most frequently in low-speed routes. The Hayes, one of the 




Fig. 75.— Split point derail 



hftmg block type, shown in Fig. 76, rests on top of the rail when 
set to stop traffic; and although it allows the rails to be continu- 
ous, It IS used largely on medium-speed and low-speed routes, 
ihe liftmg rail type, one form of which is shown in Fig 77 is so 
built that a sharp point fits against the inside of one rail and'a flat 




Fig. 76.— Hayes derail. 

riser point against the outside of the head of the outer rail when 
set to stop traffic. The sharp point derails the wheels on one side 
while the flat point hfts those on the other side high enough to 
allow the flange to clear the top of the rail. In this type both 



66 



RAILWAY SIGNALING 



track rails are continuous. Several others are built on the same 
principle, some of which have the flat point lying on top of the 
rail instead of on the side of it. The two points are connected by 
means of tie rods and are moved simultaneously into positions 



n Han n n n n 




MUj p™ 1^1 uiJ\ pir 



Fig. 77. — Morden derail. 



for clearing or derailing trains. This type is used principally on 
high-speed routes. 

43. Crossing Bars. — Crossing bars are used at interlocking 
plants to prevent a towerman from changing a line-up while a 



Fig. 78. — Crossing bars. 



car or locomotive is standing on a railroad crossing. They are 
just ordinary detector bars placed as near to the crossing frog as 
possible, one on each side of the crossing in each track. These 
bars lock the derails both normal and reversed so that they cannot 



MECHANICAL INTERLOCKING 



67 



be moved without operating the crossing bars. If a car should be 
standing on the crossing, it would be impossible to move the bar 
and hence impossible to change the derails and the signals on that 
route. 

44. Semaphore Signals. — Figure 79 shows the method of con- 
structing and operating a one-arm two-position lower quadrant 
signal. The left-hand signal is operated by a pipe line with the 




Fig. 79. — One-arm two-position lower quadrant signals. 



counterweighted lever near the base of the post, while the right- 
hand signal is controlled by a wire line and chain running through 
a wheel at the base of the post and the counterweighted lever 
more than half way up on the post. Two wires are required to 
operate the signal. The post is made of three lengths of pipe, 4, 
5, and 6 in. in diameter. 

Figure 80 illustrates a pipe and wire operated two-arm two- 
position signal. The details of upper quadrant one and two-arm 
signal construction, as recommended by the Railway Signal 



68 



RAILWAY SIGNALING 



Association, are shown in Fig. 81, a and b. The mast proper 
of the one-arm signal is 25 ft. high, made up of two lengths of 
5- and 6-in. pipe swaged together at the joints. The pinnacle, 3, 
brings the total height up to 26 ft. 8 in.- above the foundation. 
The spectacle casting, 8, has three roundels, or glasses, properly 
spaced to allow for the 45- and 90-degree positions of the signal. 
The lamp is attached to the post just behind the right-hand 





Fig. 80. — Two-arm two-position lower quadrant signals. 



roundel. The blade, 9, is made either of wood or sheet metal. 
The up-and-down rod, 11, is a 1-in. pipe fitted to the casting of 
the arm and the angle crank at the base to operate the signal. 
The upper quadrant type of construction does not need the coun- 
terweighted arm. All the appliances are attached to the post 
by means of clamps. The foundation and anchoring plans are 
also shown in the figure. 



MECHANICAL INTERLOCKING 



69 



Figure 81c represents a three-arm signal that corresponds to 
the arrangement in Scheme 3, Appendix B. A two-position 
bracket signal is shown in Fig. 82, while some of the details of 
construction of a three-arm bridge or bracket signal are presented 
in Fig. 83. Figure 84 is a cantilever attachment for a doll post. 







Fig. 81. — R. S. A. standard upper quadrant signals. 



45. Dwarf Signals. — ^Figure 85 represents a one-arm two- 
position upper quadrant dwarf signal. Attached to the operating 
mechanism is a spring that is placed under compression when the 
proceed indication of the signal is given so that if the wire line 
that operates the signal fails the blade automatically goes to 
the stop position. The blade of the dwarf signal is made flex- 
ible so that it can be struck without injury. Figure 86 is a 
Railway Signal Association upper quadrant pipe-operated dwarf 
signal. 

46. Time Lock. — A time lock illustrated in Fig. 88 is a mechan- 
ical appliance used in connection with the home signal lever of a 
mechanical interlocking plant to prevent the towerman from 



70 



RAILWAY SIGNALING 




ro-\5Qijiiiiiiiiiiui 




mr^^^^^i^ 



Fig. 82. — Two-position lower quadrant Fig. 83. — R. S. A. three-arm upper quad- 
bracket signal. rant bracket or bridge signal. 




Fig. 84. — Cantilever bracket. 



^1 



MECHANICAL INTERLOCKING 



71 



quickly changing a line-up after it has been accepted by a train. 
A heavy rack, supported vertically, is raised quickly by reversing 
the lever, and is held in that position until the lever is thrown 
towards the normal position. As soon as the lever is placed 




Fig. 85. — One-arm two-position upper quadrant dwarf signal. 

normal, however, the support for the rack is removed, and the 
rack is dropped very slowly. There is nothing to prevent the 
towerman from returning the home signal lever to normal, but 
he cannot release his latch until the rack runs down. 




Fig. 86. — R. S. A. dwarf signal for pipe connection. 



The weight of the rack actuates a double pendulum in such a 
manner that each swing of the pendulum drops the rack one 
tooth. A roller on the end of the cross-lock connected with the 
locking bed in the case of the Saxby and Farmer machine, en- 



72 



RAILWAY SIGNALING 



gages the back of the rack and prevents the lever latch from 
being placed entirely normal while the rack is up. There is a 
notch in the back of this rack located at just the point to contain 



WaZO-STOMPEO BR.- 

SPECIPICKriONS 

I BOOC OF LAMP SHALL BE NUDE OF 
NO. e SHEET STEEL TINNED. 

2.WVETS SMALL BE USED IN CONSTFU- 
CnON OF THE BODY OF THE LAMP 
FOR HOLOWe PARTS TOGETHER. . 

3. HANDLE OF LAMP SHALL BE NO. 4- 
B.W.G. STEEL WRE. I 

4. DOOR SHALL HAVE W«TtR-SHED SO 
ARRANGED AS TO PREVENT RAIN 
ENTERING THE LAMP, DOOR SHAa 
RAISE HIGH ENOUGH TO MAKE THE 
OPENING SIX AND FIVE -EIGHTHS 
(6|) INCHES. 11006. 

5. LAlJlP SHAa HAVE TOP DRAUGHT HOOI 
VBfTIUnON. (VENTILATIOH WIL i" 
GE TESTED WHEN R^UIRED AT THE S 
FACTDRT AS FOLLOWS: 'A' WIND 
VELOCITY EQUIVALENT TO EIGHTY 
(80) M.P.H. FOR TWO (2) MINUTES. 
"B' STILL AIR TEMPERATURE ONE 
HUMMED AND TEN (llO) DEGREES RWR- 
FOR TWO (2) HOURS). THE LAMP 
WIU BE REJECTED IF EITHER OF 
THE ABOVE TESTS EXTINGUISH 
THE FLAME. 

6. LENS SHALL BE ( SES. REFERENCE N0^) INCHES IN. 
DIAMETER WITH THREE AND ONE- 
HALF (3^) INCH FOCUS. 

7. LENS HOLDER SHALL BE ARRANGED 
SO THAT LENS CAN BE EASILY RE- 
MOVED AND SHALL COMPLETaY 
BWIRCLE THE LENS . 

&SOCKET NOT TO EXCEED THE DI- 
MENSIONS OF BRACKET MORE THAN 
ONE- SIXTEENTH (A) INCH AND BE 
EIGHT (8) INCHES W DEPTH, RE- 
CESSED TO FIT STANOARO LAMP 
BRACKET. (R.S. A. 1049) 

9. BACK LIGHT AND PEEP-HOLE GLASSES 
SHALL BE HELD IN PLACE BY ^1 

(11006) SCREW RE15WNING <;^ 
RINGS. 

10. INSECT SCREEN SHALL BE PRO- . 
VIDEO WHEN SPECIHED. 



FIT STANOARO LAMP 
BRACKET R.S.A.1049 




/ EXCEPT AS NOTED 
THE CONSTRUCTION 
OF LAMP ABOVE THIS 
LINE IS NOT SPECIFd 



/■note: w«n ordering appar- 

/ atus or parts shown on this 

/' plan give number and name 

appearing in l,ar€e type 

T- 



igM^^ 




■9_" BASE OF LAMP> 
o.UUKt -^ a h-^ WTTOMOF 
° 32 LAMPSOCnET 

11007 IMALLEABLE POCKET '-jse 

TD RECEIVE PWNTEO LOG OF J. 

LAMP BRACKET R.S.A.1049 



SCALE OF INCHES 




IIOOIS LAMP COMPL.WITH 5" LENS 
_l II00I6 *' *' *' SH, " 

110017 a it « 6V *' 

SEMAPHORE LAMP 

(DETAIL AND ASSEMBLY) 



I T 



■ijiiaisMfeoiaaBEaiaasiaHHiQSE 



RSA 
1100 



Fig. 87. — R. S. A. semaphore lamp. 



the roller when the rack is entirely down. The cross-lock is free 
to move when the rack is down, releasing the home lever latch 
and allowing it to finish its throw to normal. After the latch is 



MECHANICAL INTERLOCKING 



73 



in its normal position, the derail may be opened and another 
route lined up. In the case of the Style A machine the cross- 
lock is connected with one end of the rocker-link, but its action is 
practically the same. 

These time locks are so adjusted as to require from one minute 
to one minute and twenty seconds or even longer to run down. 
This means that the tower- 
man will have to wait this 
amount of time to throw the 
derail after he has thrown 
the home signal to danger. 
The length of that time would 
be sufficient to allow a train 
running at average high-speed 
at the distant signal to get 
far enough over the plant to 
be out of danger or to come 
to a stop before the tower- 
man would have time to open 
the derails, should he sud- 
denly decide to take the 
signals away from this train 
and give them to another on 
a conflicting route. 

47. Calling-on Arm. — It 
sometimes becomes neces- 
sary when a home signal is 
used for interlocking where 
block signal circuits are in 
operation, to install what is termed a calling-on arm signal. 
After a train has passed the home signal in such an installation, 
the signal automatically goes to the stop position. There are 
times while this train is making the station or other stop and 
thereby preventing the home signal from being cleared, that it 
becomes expedient to signal a following train to pass the home 
signal and proceed slowly towards the station or other point in 
the interlocked territory. To advance the second train past the 
home signal the towerman must use the calling-on arm. It is 
mounted on the same post as the home signal arm, but generally 
has a shorter blade. It is operated independently of any track 
circuit by the same kind of mechanical or power appliances as are 




Fig. 88.— Time lock. 



74 



RAILWAY SIGNALING 



used to throw the derails and switches. In c, Fig. 81, the upper 
blade governs the superior route, the middle one the inferior 
route, and the lower one may be a calling-on arm for either. 

48. Movable Bridge Couplers and Locks. — Figure 89 shows the 
four-way bridge coupler used to open and close pipe lines where 



fi 



K 



} =i 



V 




Fig. 89. — Swing bridge coupler. (Signal Dictionary.) 

they cross the ends of movable bridges. A device for checking 
the position of Hft bridges when closed is shown in Fig. 90. A 
is fastened to the bridge. The tumbler F has a notch in it that 
engages the stud B when the bridge drops into position and is 



MECHANICAL INTERLOCKING 



75 



closed. E is fastened to the bridge seat. When the bridge is 
closed, plunger D will pass through the opening on the back end of 
E. When the bridge is raised, the tumbler F pivoted at C, will 
drop in front of this opening stopping the movement of D and 
holding all signals and derails in the normal position. As soon as 
the bridge is properly locked, however, the track may be cleared. 
Devices very similar to this are used to lock swing bridges. 




3:o>-D 



Fig. 90. — Bridge lock. (Signal Dictionary.) 

49. Rules. — The following rules prepared for the benefit of 
train and motor crews and signalmen are reprinted from the 
Proceedings of the Railway Signal Association, 1914 1^ 

"Interlocking Signal Rules. — Interlocking signal rules govern the use 
of interlocking signals. 

"Interlocking signals are used to govern movements over tracks where 
there are switches, drawbridges, railroad crossings at grade and other 
conditions affecting the movement of trains. 

"Hand signals must not be accepted as authority to pass any signal 
indicating STOP, except for switching movements when the governing 
signal cannot be cleared. They must be given by the signalman from 
the ground, upon the track for which they are intended, and only after 
the train or motor which is to make the movement has been stopped, 
and the situation fully explained and understood. 

"Interlocking Signal Rules. — For train and motor crews. A signal 
indicating STOP must not be passed except as pro\dded by the Rules. 

"Interlocking signals when at PROCEED indicate the particular route 
set and show that switches are locked for the train to proceed, but not 
that the track is unoccupied. 

"Interlocking signals indicate that a movement may be made onl}^ 
within the limits of the interlocking plant. 

"Trains or motors stopped while within the hmits of an interlocking 

1 Page 120. 



76 RAILWAY SIGNALING 

plant, must not move in either direction until they have received the 
proper signal. 

"Interlocking Signal Rules. — For signalmen. If necessary to stop a 
train at a point at which clear signals have been displayed for it, sig- 
nals must be changed to give the STOP indication, but locks and 
switches must not be changed or signals cleared for a conflicting move- 
ment until the train which had accepted the indication to proceed has 
stopped. 

''A switch or facing point lock must not be moved when any portion 
of a train or motor is standing on or closely approaching the switch or 
detector bar. 

"A drawbridge must not be opened until proper signals have been 
displaj^ed. 

''During sleet or snow storms special care must be used in operating 
switches. If the men whose duty it is to keep the switches in working 
order are not on hand promptly when required, the fact must be re- 
ported by wire (or telephone) to the 

''During cold weather the levers must be moved as often as may be 
necessary to keep connections from freezing. 

".Salt must not be used on interlocked switches, or other appKances, 
except on authority of 

"Levers must be operated with a careful uniform movement. If the 
operation of a lever or other apparatus indicates a disarrangement of 
the parts, the signals must be restored to give the normal indication, 
and an examination made at once to ascertain if the parts are in safe 
and proper working order. 

"Signalmen must see that lever is latched after lever movement has 
been completed. 

"Should it be impossible to lock a facing point switch, the switch 
must be examined and spiked in proper position before train is allowed 
to pass. 

"When switches, signals and their connections are undergoing repairs, 
PROCEED signals must not be given for movement over track sections 
affected by such repairs, until it has been ascertained that the switches 
are properly set and secured. 

" Signals must not be cleared for trains to proceed except by working 
the lever provided for the purpose. 

"When a switch, movable-point frog, derail, lock, detector-bar or 
switch-locking circuit is inoperative, the signalman will be given notice 
in writing by the maintainer and will make record of same on block 
sheet. The signalman must know that each switch, frog, and derail 
is spiked for the desired route and, when practicable, locked with plunger 
so that it cannot be withdrawn, before such route is used by trains. 
The must be notified promptly of the condition of the appara- 
tus and the home signal governing movements over the route must indi- 



MECHANICAL INTERLOCKING 77 

cate STOP, and each train must be given a hand signal to proceed, 
unless other instructions are received from the 

''When a switch or movable-point frog is spiked a man must be sta- 
tioned by the section foreman or maintainer to see that such parts are 
properly set for the route indicated by the signalman, before allowing 
train to pass. The signalman must know that switch or frog is properly 
set and secured for the desired route. 

" When a home signal is disconnected, it must be fastened in the STOP 
position. 

''If there is a derailment, or a switch is run through, or if any damage 
occurs to the track or interlocking plant, the signals must be restored to 
give the STOP indication and no train or switching movement must 
be permitted until all parts of the interlocking plant and track liable to 
consequent injury have been examined and are known to be in a safe 
condition." 



CHAPTER VI 

ELECTRO -PNEUMATIC INTERLOCKING 

In electro-pneumatic interlocking plants compressed air is used 
to throw switches, signals and derails operating them by means of 
cylinders whose valves are controlled by electricity. As the 
action is quicker than is the case in the mechanical and electrical 
plants, the system finds its best application in large terminals, in 
subway and elevated lines, and in other places where there is 
frequent traffic. 




Fig. 91. — South Station, Boston, Mass. 

50. Air Supply. — At points where such plants are likely to be 
installed there is frequently an adequate supply of air already 
available that needs only to be piped to the immediate places 
where it is to be used. In case no such supply is convenient it 
becomes necessary to install a compressor, operated either by a 
gasoline engine or by an electric motor. The air is pumped into 
storage reservoirs to maintain an adequate supply, the pressure 

78 



ELECTRO-PNEUMATIC INTERLOCKING 



79 



of which usually averages about 75 lb. a square inch. A typical 
plant is illustrated by Fig. 92. 

After-coolers of the water and air-cooled type are usually 
employed to reduce the temperature of the air to normal after it 
has passed through the compressor. The storage tanks provided 
for the air are usually set low enough to collect the moisture that 
results from condensation, thus eliminating the danger of the 
freezing of the plant in the winter. The air pipes that connect 
with the storage supply and furnish the trunk Une of the piping 
system are usually about 2 in. in diameter. The branch pipes 
are usually % in. in diamteter with K-in. connections to switches 
and signals. On account of the flexibility and vibration of the 



6c/-Pass B 




Fig. 92. 



Bhw-Off 



-Diagram of typical air compressing, cooling and distributing system 
for electro-pneumatic interlocking. 



track, the connection to switches is usually made with an armored 
hose. 

The pipe is generally galvanized, and where it is laid across 
the tracks is placed a few inches beneath the surface of the 
ground; where the pipe is laid parallel with the tracks, it is usually 
supported a few inches above the ground on wooden stakes or 
concrete piers. Usually two routes are provided to each switch 
and signal to insure an air supply in case of failure in some part of 
the pipe line. Gate valves are located in the mains and stop- 
cocks in the branches in order to be able to shut off the air and cut 
out a section should it become necessary to repair a pipe or 
break a connection to a switch or signal. 

Expansion in the mains is provided for by bends or by sliding 
expansion joints. Branch pipes should come out of the tops of 



80 RAILWAY SIGNALING 

mains, thereby eliminating the possibiHty of having water drawn 
over if the main should not be properly drained. An auxiliary 
air reservoir is usually provided near each switch or signal to 
furnish an immediate supply of air and to provide a sump for any 
water that may have collected in the pipe. A strainer is placed 
in the line where it joins the operating equipment to clear the pipe 
of any moisture or sediment that may accumulate while the air is 
passing through. All of the reservoirs along the line are so con- 
structed that the water may be blown out as often as desired. 

51. Electricity. — The supply of electricity for most electro- 
pneumatic plants is furnished by storage cells, although a few have 
been built for 110-volt alternating current. Six or seven cells 
of the lead type or 12 of the Edison, furnishing approximately 12 
volts, constitute the main battery. The usual practice is to have 
a gasoline engine or an electric motor drive a generator to charge 
the batteries. To guard against failures, this equipment of 
engine, generator and batteries is generally duplicated. The best 
place to install such equipment is in the lower part of the tower 
where the signalmen can take care of it. 

52. General Sequence in Power Interlocking. — From consid- 
erations of safety it is fundamental in power interlocking that the 
steps involved in the throwing of a switch and the clearing of a 
signal should take place in the following sequence : 

1. In providing assurance that conditions are right for the 
throwing of the switch. The mechanical locking insures that 
no conflicting routes are set up and that no signals are cleared for 
movement over the switch. The detector locking, which electri- 
cally locks the switch levers, insures that no train is within a 
certain distance of the switch. Thus the lever is mechanically 
and electrically unlocked if conditions are right. When detector 
locking is not installed, detector bars operated by the switch 
movement provide mechanically against movement of the switch 
while a train is over the detector bar. 

2. In making a preliminary lever movement which mechan- 
ically locks conflicting levers, and effects circuit changes which 
cause the switch to be thrown. 

3. In receiving an indication that the switch has been thrown 
and locked. 

4. In completing the lever stroke, which frees the mechanical 
locking for other lever movements. 

5. In throwing the signal lever which clears the signal. No 



i 



ELECTRO-PNEUMATIC INTERLOCKING 



81 



indication is required that the signal actually clears since it 
would not be an unsafe condition if it should fail to clear. 

After the train has accepted the signal and passed through the 
route, it may be desired to change the route for other train move- 
ments. In order to do so it is necessary to : 

1. Restore the signal to stop by preliminary lever movement. 

2. Receive an indication that the signal has gone to the stop 
position. 

3. Place the lever in full normal position, thus freeing the 
mechanical locking for other lever movements. 

A description of the different parts of the electro-pneumatic 
system follows with an explanation of how each functions in the 
sequence outlined above. 

53. Interlocking Machine. — Figure 93 shows a Model 14 elec- 
tro-pneumatic interlocking machine. The operating levers are 




Fig. 93. — Electro-pneumatic interlocking machine. 



arranged in a row across the front of the machine and are num- 
bered from left to right. Those turned upwards are switch levers 
and bear odd numbers, while those hanging vertically downwards 
are signal levers and bear even numbers. In its normal position 
the switch lever stands 30 degrees to the left of the vertical, 
and when reversed it stands 30 degrees to the right of the vertical, 
moving through an angle of 60 degrees. One switch lever may 
control one, two and sometimes three switches, derails or movable 
point frogs. The signal lever points vertically downwards 
when normal; thrown 30 degrees to the left it serves to clear its 
corresponding signal or the selected one of a group of signals; 
thrown 30 degrees to the right it clears another given signal or 
selected one of a group, for train movement in the opposite di- 



82 



RAILWAY SIGNALING 



rection. All signals that may be controlled by a given lever, 
however, must be those that govern movements over a common 
section of track. The ability to control more than one switch, 
or more than one signal, from a given lever saves a great many 



i: 



r 




, « ^^^^^BH^^SH^ 




' ^ ■ ■'^ilii^fe^Si^B 


r*^ 


4 


^^ 





*' 



Fig. 94. — Electro-pneumatic interlocking machine. Case removed. 

levers, makes it possible to erect a smaller and cheaper tower, and 
reduces the number of operators required on large plants. 

Each lever of the machine is fastened to a horizontal shaft that 
extends from the front to the back of the machine, and is equipped 




Fig. 95. — Electro-pneumatic interlocking machine. Rear view. 



with a latch that is operated by turning the handle. As the lever 
is rotated, the latch moves over a notched quadrant on the front 
of the machine. In order to move a lever it is first necessary to 
turn the handle and thus to raise the latch out of its notch. 



ELECTRO-PNEUMATIC INTERLOCKING 



83 



The front portion of each lever shaft operates one of the lock- 
ing bars of a mechanical locking bed, as shown in Fig. 98. This 
locking bed is similar to that used on a Saxby and Farmer ma- 
chine, except that it is constructed on a smaller scale. A segmen- 
tal gear fitted to the shaft meshes in a rack cut on the under side 
of the locking bar. As the shaft is rotated the bar is shifted. 
The rear section of the shaft carries the segments that engage the 



Bevel Gear 
Drive f^ci ho ^ 

M ECHANICAL LOCKlHG ^ ,. " ' 
Lever TTTTTPC,., ..,. ■^^¥" 
Handle. 



Locking 
5egmenf 



• Normal IneHcahon 
Magnet 




Arms and Links for 
Dnvinof Lower Secf ion 
of^ny Roller of fhe 
Machine from Another 
Lever When Required, 



Switch lever complete. 



indication latches. These latches are dropped and locked by 
gravity and are raised and unlocked by the armatures of the 
electro-magnets. Projections on the segments are engaged by 
the latches unless the magnets are energized at the proper time. 
There are two indication magnets for each switch lever, the 
normal and the reverse. The segments are arranged to provide 
detector locking and, after the preliminary movement, to restrict 
further lever movement until the switch indication has been re- 
ceived. Figure 97 gives a diagram of a switch lever and a re- 



84 



RAILWAY SIGNALING 



verse indication segment. Each signal lever has one magnet, 
often called the lock magnet. Its function is to prevent the plac- 
ing of the signal lever in the full normal position until the indica- 
tion is received that the signal has gone to the stop position. 
Figure 98 shows a signal lever in its ^^L" (reversed) position. 
Figure 99 gives a diagram of its positions and operations. 



\ \ IMcahng / 



Posifiori'i 




/Rubber Rolhr 

li"clia. Turnina 

ihroughllO^ 

\ (£)Defween Indicahng ("js- , ' 
Quick Swii-ch q\^\ ! y^ 





(a) 



Fig. 97. — Diagram of a switch lever and its operation. 



As shown in Figs. 96 and 98, a set of bevel gears near the middle 
of the lever shaft serves to transmit motion to a vertical shaft. 
This vertical shaft forms a part of the ''combination" or circuit 
controller that is used to govern the movements of switches and 
signals. It is encased in a hard rubber roller upon which are 
mounted phosphor bronze bands that turn between flat phosphor 
bronze springs extending out from a vertical plate of moulded 
insulating material. These rollers have a number of fine longi- 
tudinal saw-cuts which receive and hold the turned-in ends of the 



ELECTRO-PNEUMA TIC INTERLOCKING 



85 



contact bands as illustrated in Fig. ^7d. The contact bands as 
well as the contact springs are made in several lengths so that it 
is possible to arrange a circuit to open or close at any desired 
position of the operating lever. The adjustment of these circuit 
controllers is made much easier by the fact that the roller is con- 
structed to turn through twice as many degrees as the lever shaft 
by the ratio of the bevel driving gears. 



Bevel 6<?ar 

Drive Ratio 

I to 2 



Clamfp 



Coupling \ 
tIECHAHICAL LOCffiNG 
Lock 5.ar Cross Lock 



Locking 
Segment 



•Lock Magnet- 




Key Ways 
Key Femo^ec^ 



Lower Section 
of Roller C 
Here Driven 
by Roller A 



Arms anci Links 
for Dn ving L ower 
Section of Any Roller^ 
of the Machine from 
A no the r Lever When I 
Requir(c 



Fig. 98. — Signal lever complete. 



In an earlier type of the machine, the contact rollers were 
made an intermediate part of the lever shaft; and the insulating 
plate supporting the contact springs was held in a horizontal 
position below it. This machine is called the horizontal roller 
type, while the Model 14 machine is known as the vertical roller 
type. 

On the end of each switch roller is a hard rubber collar, or 
sleeve, on which are mounted two contact bands that operate 
between springs mounted on the same insulating plate. This 
collar or sleeve does not turn with the shaft until the lever has 



86 



RAILWAY SIGNALING 



moved through an angle of 50 degrees, being held in its original 
position by a toggle spring. When the shaft has turned five- 



io' UJ 0®. ' 








/::::^ 




® 



Cb) 



-# ® ® 
® ® 



®^-i;""® 



® 



CO 



Fig. 99. — Diagram of a signal lever and its operation. 



TERMINAL SCRLWS 



CONTACT BAND 
CONTACT SPRING 



WIR£ TERMINAI. 




[channel, bar CARRYING 

^combination plates and 
Ibearings for rollers 



Fig. 100. — Rollers, contact springs and quick switches. 

sixths of its throw, however, this collar is also forced to turn, and 
as its toggle passes dead center it snaps over to its opposite ex- 



ELECTRO-PNEUMATIC INTERLOCKING 



87 



treme position. This arrangement is called the ''quick switch," 
and is illustrated in Figs. 96, 97 d, and 100. 

The working parts of the machine are enclosed in an enameled 
steel case to prevent the accumulating of dust and the tampering 
with the parts by unauthorized persons. 

54. Mechanism for Throwing Switches and Derails. — The 
switches are operated by means of switch and lock movements 
similar to the ones used in mechanical interlocking, the actuating 
power, however, being compressed air. The piston rod of the 
air cylinder connects directly with the slide bar of the switch and 




Fig. 101. — Electro-pneumatic switch and lock movement. 



lock movement, as indicated by Fig. 101. The stroke of the pis- 
ton rod and of the switch and lock movement is 12 in. The first 
2 in. of the stroke unlocks the switch and throws the detector 
bar, the next 8 in. throws the switch, and the last 2 in. locks 
it in its new position. 

The switch cylinder and piston operate very much like the 
cylinder and piston on a steam engine. On the side of the switch 
cylinder, but sometimes separately mounted, is a ^'D" slide 
valve. Figs. 102 and 103, which opens and closes the inlet and 
exhaust ports to the cylinder. This slide valve is driven by two 
small shifting pistons, one on each side, impelled by compressed 
air. The flow of air behind these pistons is, in turn, controlled 



88 



RAILWAY SIGNALING 



by the normal and reverse electro-magnets. Provision is made 
for locking the slide valve by a lock that is operated at right angles 
to the motion of the sHde valve, and is actuated by a third piston. 
Air pressure behind the lock piston is controlled by the lock 
magnet. The lock piston also opens and closes a valve which 
controls the supply of air to the valve body. Thus it is seen 
that the switch valve has three magnets, normal, reverse and 
lock. To throw a switch it is necessary to energize the lock 
magnet in order to unlock the slide valve and admit air to the 




Fig. 102. — Switch valve and magnets. 



valve body, and to deenergize one of the control magnets and 
energize the other in order to shift the slide valve. When the 
controlling lever is in full normal or reverse position, current is 
maintained on the corresponding control magnet, but is cut off 
from the lock magnet. 

The operation of an electro-pneumatic magnet may be under- 
stood from an inspection of Fig. 104, which shows the type used 
on a signal. Between the armature and the coil are three short 
springs that keep the armature raised when the magnet is not 
energized. Attached to the armature and running down inside 
the coil is the armature stem, the lower end of which is so bevelled 
as to seat itself and hold the exhaust post closed when the mag- 



ELECTRO-PNEUMA TI( ' INTERLOCKING 



89 




•Air Inlet. 



Oil Plug, 



Cylinder Head.- 

Unlock Piston, 

Lock Piston. 

Locking Tappet, 

Stuffing Box 



^♦-Exhaust Port, 
Exhaust Valve. 
Inlet Valve. 

D -Valve. 
Shifting Piston. 




^^iR Inlet. 
Fig. 10.3, Part 1. — Switch valve and magnets. 



90 



RAILWAY SIGNALING 



net is energized. The lower end of this stem engages the stem 
of a pin valve. Air under pressure comes into the air supply 
pipe. When the coils are energized the pin valve is unseated 
and the exhaust valve is closed, allowing air to pass from the air 
supply pipe directly into the pipe leading to the cylinder. 



Oil Plug. 



Cylinder Head 

Unlock Piston^ 

Lock PisTONr 

Locking Tappet. 

Stutfing Box. 




Exhaust Port. 
Exhaust Valve. 
Jn LET Valve. 

,D-V^LVE. 

iH/FTiNG Piston. 



>AiR Inlet. 
Fig. 103, Part 2. — Switch valve and magnets. 

55. Indication Circuit Controller. — Mounted on the switch 
movement and actuated by a cam plate attached to the slide bar 
is the indication circuit controller, Fig. 105. It is enclosed in a 
cast iron case, and consists of slides of insulating material bearing 
contact springs that move between contact points mounted on 
either side. The motion transmitted to the slides is such that 
one makes its movement before the switch is fully unlocked, and 
remains stationary while the switch is being thrown; the other 
makes its movement after the switch is locked in the opposite 
position. 

56. Indication Relays. — Located in the tower is one polarized 
relay for each switch lever. A pair of small wires connect each 
relay to a switch circuit controller. When the switch is normal 



ELECTRO-PNE UMA TIC INTERLOCKING 



91 



and locked, current of a certain polarity is fed to these wires 
through the indication circuit controller; when the switch is 



ADJUSTMENT 

ARMATURE 



-BRASS TUBE 
-OUTER POLE 
•INNER POLE 
-INSULATION 
-HELIX 




-BACK STRAP 
-JAM NUT 



'TO CYLINDER 



Fig. 104. — Cross-section of pin valve. 

unlocked or open, these wires are disconnected from their source 
of energy and are connected together; when the switch is reversed 





P'P^^^^^^^^^I 




i^^^^f^ 








^■^M 

J 

• i**^ 







Fig. 105. — Pole-changing indication circuit controller. 

and locked, current of a polarity opposite to that used for normal 
indication is fed to the indication wires. Thus the relay in the 



92 



RAILWAY SIGNALING 



tower is made to repeat the position of the switch. Unless the 
switch is fully locked the relay contacts will be open. When 
the switch is normal, one set of polar contacts on the relay is 




a 
o 
o 



closed; when the switch is reversed, the other set of polar contacts 
is closed. Current for picking up the switch lever indication 
magnets is taken locally through both neutral and polar con- 
tacts of the polarized relays. Thus the indication magnets can 



ELECTRO-PNEUMATIC INTERLOCKING 



93 



receive current only when the relay is picked up and the proper 
polar contacts are closed. 

The quick switch previously mentioned serves to close the local 
indication circuit to that magnet which should be next picked 




o 

a 

1 1 

OS L, 

_r ^ 

o 
o 



up and to open the circuit to the other magnet. As normal indi- 
cation is received and the lever stroke completed, the quick 
switch opens that circuit and closes the circuit to the reverse 
indication magnet, which will be the next one to be picked up. 



94 RAILWAY SIGNALING 

57. Detector Locking. — At the extreme end of the lever 
stroke, the magnet which has been disconnected by the quick 
switch from its source of current coming through the indication 
relay, is connected by the ''X" or '' Y" springs to another source 
of energy controlled by the track relay of that section in which 
the switch is located. Thus the indication magnets also serve as 
detector magnets, for the levers in full normal or full reverse 
position are locked in place unless the corresponding magnet can 
be energized. A switch could not be thrown with a train in that 
particular track section because the track relay would be open, 
interrupting the flow of current. The current for this circuit is 
also passed through a normally open contact actuated by the 
lever latch so that the magnet is not continually using current. 

58. "SS'^ Control. — Current from the signal levers for clearing 
the different signals is carried over contacts on the indication 
relays of those switches in the route governed. This arrangement 
provides assurance in addition to the mechanical locking that all 
switches are properly set in order to get a clear signal and makes 
certain that no switches have been improperly set by hand after 
the indication was received, a point which would not be checked 
by the mechanical locking. 

59. Throwing a Switch. — When the lever is in its normal or 
reverse position and its latch is lifted, it completes the circuit 
from the track relay through the latch contact energizing the 
magnet of the normal or reverse indication segment latch, pro- 
vided there is no train to short-circuit the track relay and drop 
its armature, as shown in Fig. 106. This unlocks the lever and 
allows it to be rotated. In following the cycle of throwing a 
switch, the switch is considered to be in its normal position and 
will be thrown from normal to reverse. 

When the lever shaft has been turned 10 degrees to the right, 
the contact is made on the hard rubber roller that energizes the 
lock magnet at the switch cylinder, unlocking the slide valve in 
the cylinder. The further rotation of the lever shaft up to a 
total angle of 373-^ degrees makes other contacts on the hard 
rubber roller, deenergizing the normal magnet and at the same 
time energizing the reverse magnet. This permits the air to 
escape from behind one of the small pistons and to exert a pres- 
sure behind the other so as to move the slide valve and admit air 
behind the piston of the switch cylinder. This pressure causes 
the piston to travel the length of its stroke throwing the switch 



ELECTRO-PNEUMATIC INTERLOCKING 



95 




a T3 
o a 



96 



RAILWAY SIGNALING 




I 



ELECTRO-PNEUMATIC INTERLOCKING 



97 



and locking it by means of the switch and lock movement. When 
the switch is thrown to its proper position, the circuit is completed 
through the switch indication circuit controller picking up and 
reversing the polarized indication relay and energizing the reverse 
indication magnet, thereby raising the segment latch and allow- 
ing the lever to finish its stroke to the extreme right. The lock 
magnet is now deenergized, but the reverse control magnet re- 
mains energized until the switch points are thrown back. 

When the movement of the lever is being completed, it operates 
the quick switch, which opens the indication circuit for the re- 
verse indication magnet and closes the corresponding circuit for 




DETECTOR WIRE TO TAKE + BATTERY 
THROUGH NECESSARY TRACK RELAYS 
AND ROUTE LOCKING RELAYS 



NORMAL CONTROL MAGNET^ 
MAGNET^ 



INDICATION CIRCUIT CONTROLLER 



INDICATION WIRES - 



:^: 



SIGNAL CONTROLS 



LOCK WIRE ■ 



REVERSE CONTROL^ 



NORMAL CONTROL-^ 



12 VOLT D C POWER MAINS FOR THE COMPLETE SYSTEM 




-Diagram of complete control, indication and locking circuits for 
single switch with D.C indication. 



Fig. 110. 



the normal magnet, although the latter magnet cannot receive 
any current until the polarized relay has responded to the next 
movement of the switch. As the quick switch opens the indi- 
cation circuit, the "Y" springs close the circuit from the track 
relay to the reverse indication magnet through the latch contact. 
When the latch drops into its notch, the latch contact opens, thus 
leaving the magnet on open circuit to economize on current. 
Should it later be desired to move the switch back to normal it 
would first be necessary to raise the lever latch which closes the 
detector circuit for the reverse magnet in order to raise the indi- 
cation latch and unlock the lever. If a train is on the track 
circuit, the track relay contacts will be open, the magnet cannot 
be picked up and the lever is locked in place. Complete move- 



98 



RAILWAY SIGNALING 



ment from reverse to normal is exactly similar to that described 
above. 

Only during the time when the lock magnet on the switch is 
energized is air admitted through the slide valve into the switch 
cylinder and the pressure maintained. When the lock magnet 
is deenergized not only does it lock the slide valve, but also it cuts 
off the supply of air to the slide valve chamber and consequently 
to the switch cylinder. This arrangement avoids the waste of air 
that would occur by leakage if the pressure should be maintained 




Fig. 111. — Two-arm electro-pneumatic dwarf signal. 

constantly in the cylinder. Figure 110 is a diagram showing 
complete control, indication, and locking circuits for a single 
switch with direct current indication. 

60. Signal Operating Mechanism. — The air cylinder that 
operates a high signal is usually placed at the base of the pole. 
The up-and-down signal rod operates inside the pole and is 
connected to the piston of the air cylinder by a balance lever. As 
the spectacle casting is counterweighted causing the signal to go 



ELECTRO-PNEUMATIC INTERLOCKING 



99 



to stop by gravity, the air is used only to clear the signal, thus 
requiring merely a single acting cyHnder. An electro-magnet 
fastened to the signal cylinder controls the movement of the air. 
There is a circuit breaker on the signal cylinder that gives an 
indication only when the signal is at normal. There is no indi- 
cation when the signal is cleared. The stroke of the piston is 
43^^ in. and the diameter of the cylinder is 3 in. 

In the construction of the dwarf signal, shown in Fig. Ill, the 
up-and-down rod is attached directly to the signal cylinder; the 
piston remains stationary. As the air is admitted to the cylinder 
by means of an electro-magnet, the cylinder itself moves upwards 




9P%±^'-mo. flectnc- 



Contacts 



Signal lever 
Morrncfl 

Fig. 112 



Diagram of complete signal control and indication circuits; lever 
and signals normal. 

clearing the signal, but compressing a coil spring on the up-and- 
down-rod. As soon as the air is released, the coil spring restores 
the signal to normal. A pair of contact springs placed on the side 
of the air cylinder acts as a circuit breaker and completes the 
circuit when the signal is normal. The stroke of the dwarf signal 
is 23-^ in. The diameter of the piston is 3 in. the same as the 
high signal. 

61. Operating a Signal. — For the purpose of explanation it will 
be assumed that the signal is in its normal position. The lever 
may be turned to the left or right as the case may require. 



100 



RAILWAY SIGNALING 



After it has been rotated through an angle of about 25 degrees, 
contact is made by the bronze band on the hard rubber roller 
completing the circuit to the electro-magnet at the signal cylinder 
admitting the air and moving the piston rod to clear the signal. 
To reverse the operation, the lever is rotated a short distance 
thereby breaking the circuit to the electro-magnet at the signal 
cylinder and releasing the air that holds the signal clear. Before 
it can be restored to normal the signal must go to the stop position 
so as to make contact with the circuit breaker to unlock the lock 
magnet on the lever shaft. Figures 112 and 113 show a signal 
lever and its circuits. 



Batferj^ Mams ofSi/sfem, 



isR 




"— #1-^ 



y^''''Tbcirc/rcuTf 



Lever Contact Leyer y 
ior tlainfaining '>^^'"'' ^y 
Lock on Open 



Circuit Ndrmallg 



Circuit Controller on 
Signet! Movement 



Operatma.- 
Contacts 




Switch Lever 



Signal Lever 
to Rigrht 

Fig. 113. — Diagram of complete signal control and indication circuits; lever 
and one signal reversed. 



The electro-magnets that control the segment latches on the 
back end of the lever shaft are wound to a resistance of 130 ohms. 
As these are energized for very short periods during the rotation 
of the levers, their total consumption of current is comparatively 
small. The electro-magnets on the switches and signals are 
energized for longer periods, however, and consume more cur- 
rent. One magnet on the switch cylinder is energized all the time 
and the magnet on the signal is energized during the time it indi- 
cates proceed. To reduce the amount of current as much as 
consistent, signal coils are wound to a resistance of 400 ohms. 
No. 16 wire is used for conductors except the two mains, where 



ELECTRO-PNEUMATIC INTERLOCKING 101 

not over No. 9 is necessary. The five wires leading to a switch 
are put in a cable with different colors for each wire. These wires 
are laid in trunking to protect them from the weather and from 
mechanical wear. 

62. Advantages. — As the main function of the levers in an 
electro-pneumatic plant is to make and break circuits, the lever 
equipment is much lighter and much more compact than that in 
a mechanical plant; consequently, it requires much less space to 
house the plant and fewer men to operate it. 

As the connections between the levers and the functions they 
operate are made by wires, a great deal of space is saved for build- 
ings and tracks that would be required for pipes if mechanical 
equipment should be used. It is easily adapted to any kind of 
yard conditions where there are sharp curves, complicated 
switches, and movable point frogs. 

Since the movements of the switches and signals can be very 
quickly made, train movements in busy terminals are subjected 
to a minimum of delay on account of interlocking. 

The many ways of checking and locking and guarding against 
plant failure and consequent danger promote safety in train 
operation. 

On account of the adaptability of the plant, more signals and 
switches can be thrown with a single lever than can be done with 
a mechanical plant. 



CHAPTER VII 

ELECTRIC INTERLOCKING 

The source of power used to operate an electric interlocking 
plant generally consists of 110-volt storage battery with its 
charging unit. During the past 20 years, direct current has been 
used almost exclusively to operate electric interlocking, but a few 
plants have been installed that employ alternating current. The 
interlocking plant is such a vital part of a railway system that an 
unfailing source of power such as a storage battery is generally 
considered necessary. The levers in the interlocking machine 
are operated by hand, but their only purpose is to make and 
break, in the proper sequence, contacts in the circuits that supply 
current to the motors which operate derails, switches and signals. 
A large percentage of plants now being installed are electric, for 
electric interlocking is well adapted to the operation of all types 
of yards, terminals and crossings under every traffic and climatic 
condition. 

THE GENERAL RAILWAY SIGNAL COMPANY SYSTEM^ 

63. Electricity. — The current for operating the switches and 
signals of the General Railwaj^ Signal plant is generally furnished 
by a 110-volt storage battery which is composed of 57 cells of the 
chloride accumulator (lead) type or 92 cells of the Edison type. 
Where the chloride accumulator type is used, the battery should 
have sufficient ampere-hour capacity to operate the plant seven 
or eight days, and where the Edison type is used the capacity 
should be sufficient to operate the plant four or five days. It 
is customary to provide space in the lower part of the interlocking 
tower for the storage battery with its charging unit. The battery 
is usually charged by a generator driven by an electric motor or 
by a gasoline engine, but in a few cases it is charged by a mercury 
arc rectifier. 

64. Operating Switchboard. — Figure 114 represents an oper- 
ating switchboard w^here all functions in the plant are con- 
trolled by a single circuit breaker. The apparatus mounted on 

* General Railway Signal Handbook, "Electric Interlocking." 

102 



ELECTRIC INTERLOCKING 



103 



the board consists of the cross protection circuit breaker with 
its indicating red lamp, a polarized relay, a ground lamp and 
switch, and a voltmeter and ammeter. 




Fig. 114. — Operating switchboard. 



65. Interlocking Machine. — Figure 115 represents a per- 
spective of a Model 2 interlocking machine, while Fig. 116 
shows a section parallel with the levers. This type of machine 



104 



RAILWAY SIGNALING 




Fig. 115. — Model 2 unit lever type interlocking machine. Lake Street Interlock- 
ing Plant, Chicago Terminal, C. & N. W. R'y- 



LOCRINO PLATES 



INDICATION 
[SELECTOR 




Fig. 116. — Cross section of Model 2 unit lever type interlocking machine. 



ELECTRIC INTERLOCKING 



105 



requires less room to house than the mechanical and fewer op- 
erators to manipulate the levers. There are also more checks 
to guard against failure, for it has both electrical and mechanical 
locking with provision for safeguarding against false indications. 
Figure 117 represents a switch lever used in this system of 
interlocking. Figure 117(7 shows the lever in the normal position. 
The lev^er is moved a short distance horizontally to operate first 
the mechanical locking and then the switch. The movement is 
checked in the reverse indication position, shown in Fig. 1176, 




^m 



I— I 



Fig. 117. — Switch lever, unit type. 

until the indication current comes in from the switch and releases 
the lever for movement to its full reverse position. 

There is a vertical locking system in the front of the machine 
very similar in design to that on the Style A machine. A 
typical arrangement of this locking is shown in Fig. 118. V in 
Fig. 117a, connects with a tappet in this locking bed. The roller 
on the upper end of V rolls in a slot U in the lever ho&y. When 
the lever moves from 1 to 2, the tappet is raised one-half of its 
stroke and locks by means of the mechanical locking any levers 
that operate conflicting functions. When the lever moves from 



106 



RAILWAY SIGNALING 



2 to 4, the tappet remains stationary, but the contact block Z 
connected to the lever by the rod W breaks contact with springs 
Y-Y and makes contact with springs X-X. This throws the 

batteries into the circuit to 



^ r' ' II II 'I 'I II M M 



operate the switch. The 
lever cannot be pulled out 
any farther until it is un- 
locked, the operation of 
which is explained as 
follows : 

When the lever moves 
from 1 to 2, the projection 
M strikes against K on 
indication latch L, tilting 
the latch so that as the 
lever is pulled out farther, 
the projection J will engage 
the tooth Q, As the lever 
moves from 2 to 4, the tooth 
Q meshes with the teeth on 
cam N causing it to turn 
on its axis. This rotation 
causes dog P to be thrown 
under the end of latch L, 
holding the latch so that 
when the lever moves to 
position 4, the tooth Q 
strikes projection J pre- 
venting any further move- 
ment until the switch is 
thrown and indication 
given. The indication 
current through indication 
magnet / lifts the armature 
T causing plunger R to 
strike the dog P which 
turns to release latch L and 
unlocks the lever for final movement from 4 to 5. The movement 
from 4 to 5 allows the tappet to complete its throw and unlocks 
sufficient levers to complete the line-up. If the lever moves 
beyond 3, it cannot be advanced beyond 4 nor returned beyond 2 




1^ 

bD . 



SB 



ELECTRIC INTERLOCKING 



107 



unless an indication is given. Such an indication cannot be ob- 
tained until the switch movement is complete, either entirely 
open or entirely closed. 

Swf itch Mechanism 

Mam Common . ^ 11011. 

krmarure 




Battery 



Lever Full riormal 
A- AT REST- NO CURRENT FLOWINO 



Switch Normal 



^ 



ymiiihi^ — D- 



52 



as 



Lever at Re.\iers^ 

Indicating Position 

0-OPERAT»t4G 



^Ul/lr— I 




Switch leaving 
Normal Position 



HiliHIh 






^ 



Lever at Reverse 
Indicatinij Position 

C- INDICATING 



m— I 




Switch Reverse 




Lever Full Reverse 
D - AT REST - NO CURRENT FLOWING 



tch Reverse 



Fig. 119. — Simplified circuits for Model 2 or Model 4 switch machine. 



66. Switch Lever Wiring. — The movement of the switch is 
controlled by three wires — a main common wire on which the 
battery is located, and a normal and a reverse control. These 



108 



RAILWAY SIGNALING 



control wires are also used for giving indications, the normal control 
for reverse indications and the reverse control for normal indica- 




jffim 



llrL 










CO CO 



4- 



3+ 



tions. The two control wires are connected to opposite springs 
of the circuit controller. 

67. Model 2 Switch Machine. — When the lever is moved to 
position 4 in Fig. 117a, the circuit is made through the controller 



ELECTRIC INTERLOCKING 



109 



contacts and current flows from the plus or operating bus bar 
through the safety magnet >S, Fig. 120, through the indication 
selector and controller contacts and through the reverse control 
wire to the switch motor. The return is by the main common. 
This causes the Motor A, Fig. 122, to operate the switch as 
follows: The armature of Motor A is connected by a series of 
gears to main gear Di. Pivoted to the frame is a cam crank E 
actuated by a stud on the main gear Di. Driving rod G, con- 
nected to this stud, operates a tee crank H, one arm of which is 




Fig. 121. — Model 2 switch machine. 



connected by the detector bar driving link iV to a straight bar 
compensator that operates the detector bar. The other arm of 
the tee crank H is connected to the lock plunger /. In the newer 
installations, however, the detector bar is frequently omitted 
and the track circuit substituted, as will be seen in a later 
chapter. 

Fastened to the lower arm of the cam crank E is rod J that 
shifts the switch points. B is a pole changer that is operated by 
a rod M connected with the pole changer movement L, after 
lock plunger / has passed through the lock rod K. The lock 



110 



RAILWAY SIGNALING 



plunger I also passes through a hole in the flattened portion of J 
giving additional safety. 



M N 



DETECTOR BAR 
CONNECTIOM 




Fig. 122.- 


-Model 2 


switch machine. 


A Motor 




H Lock Crank 


B Pole Changer 




I Lock Plunger 


C Friction Clutch 




J Throw Rod 


Di Main Gear 




K Lock Rod 


D2 Intermediate Gear 




L Pole Changer Movement 


E Cam Crank 




M Pole Changer Connecting Rod 


F Stud on Main Gear 




A^ Detector Bar Driving Link 


G Driving Rod 




Pin 



The main gear Di makes one complete revolution while 
opening or closing the switch points. During the first third of 



i 



ELECTRIC INTERLOCKING 111 

the revolution, the lock crank H is shifted, raising the detector 
bar and pulling the lock plunger I out, unlocking the switch; 
during the second third, the switch is thrown; and during the 
last third, the detector bar is lowered, the switch is locked, 
throwing the pole changer. The pole changer is thrown as soon 
as the plunger / passes through lock rod K. This disconnects the 
motor from the reverse control wire and closes contacts which 
connect the motor to the reverse indication wire. The mechan- 
ism is so constructed as to allow the armature to continue to 
run for a short time due to the momentum it had as a motor. 
The motor then becomes a generator driving indication current 
from the positive terminal through the main common, polarized 
relay, indication magnet, indication selector contact, lever 
contact, reverse indication wire and pole changer contact back 
to the armature which is negative when the motor is running as 
a generator. This lifts armature T and the plunger R, Fig. 1176, 
and disengages the latch L and allows the lever to finish its move- 
ment. This is called dynamic indication. The generator stops 
in a very short time, for driving this current acts as a ''snubber." 

The motor is a series-wound four-pole motor. For operating 
a single switch the four field coils are usually connected in series, 
but for operating more than one set of switch points, as movable 
frog points, the coils are divided into two sets of two coils each in 
series, and the two sets are connected in multiple. This con- 
nection gives the machine more power. The pole changer 
automatically disconnects the motor from the battery after a 
switch movement and at the same time reverses the armature 
terminals for indication purposes, thus leaving the motor con- 
nections in the proper position for the next operation. The 
reversal in the direction of rotation of the motor is accomplished 
by reversing the direction of current flow through the armature. 

The contact block may be shifted also by means of two sets of 
solenoid magnets, Fig. 123. If any obstruction, such as snow or 
ice on the track, will not allow the switch points to fit snugly 
against the rail, the direction of the current through the motor 
may be reversed by shifting the lever between 2 and 4, reversing 
the direction of the current through the solenoids; and the switch 
may then be thrown in the opposite direction. If this movement 
back and forth be repeated a few times, the obstruction may 
frequently be removed. There are fuses on the control wire 
line of such size that in case a switch should stick or the armature 



112 



RAILWAY SIGNALING 



could not rotate for any reason while the current is applied, the 
fuses would melt before the motor would burn. 

To guard against a false indication from a short-circuit between 
control wires while the battery current is flowing through the 
motor to move the switch, a safety magnet S, Fig. 120, is mounted 
beneath indication magnet /. The armature T of magnet I 
rests directly on the poles of S. Magnet S is in the battery 
circuit, and during the time the current is flowing to the switch 
motor, the armature T is held so firmly to ^ that it cannot be 
drawn to I and a false indication given. 




Fig. 123. — Pole changer for Model 2 switch machine. 

The safety magnet protects against the possible receipt of 
an improper indication due to an accidental cross between 
control wires during the time when the current is flowing through 
the lever contacts to operate the function. From the time when 
the lever is moved to the new operating position until the movement 
of the switch machine is completed, the indication selector further 
insures against the possible receipt of an improper indication. 
At all other times protection against improper operation and 
indication is secured by means of the polarized relay. If there 
should be a foreign current flowing through the reverse control 
wire when the switch is normal, the armature of the polarized 
relay would operate to open the circuit breaker and disconnect 
the battery from the machine. If the foreign current should 
flow through the reverse control wire only when the battery 



ELECTRIC INTERLOCKING 



113 



is flowing through the normal control, the safety magnet would 
prevent the indication magnet from operating and at the same 
time the polarized relay would operate to disconnect the battery. 
68. Model 4 Switch Machine. — Figure 125 shows two views 
of the Model 4 switch machine. The motor is connected to a set 
of intermediate gears that drive the cam gear D. On the upper 
side of Z) is a cam slot that engages the roller on the end of the 
locking bar F. A link on the end of the locking bar connects 
with a straight bar compensator that operates the detector bar. 
The locking dogs H are so arranged on the locking bar F that when 
one dog has been withdrawn to unlock rod /, the other dog will 
not enter its slot until the switch points have been thrown to 



u 




Fig. 124. — Model 4 switch machine. 



the opposite side. A locking bolt L operated by the cam move- 
ment engages the throw rod J and also locks the switch in both 
open and closed positions, giving additional safety to the opera- 
tion. To operate the pole changer of the Model 4 machine 
there is a tripper arm N which engages with a cam either on the 
upper or lower side of wheel D after the switch points have been 
shifted and locked in position for traffic. The tripper arm 
operates contact blocks ^i and ^2, Fig. 126. Roller U engages a 
cam slot on the locking rod F and operates the arm T2 and the 
contact arm V. 

69. Model 5 Switch Machine. — Figure 127 represents a plan 
and section of a Model 5 direct-current llC-volt switch machine 
complete with adjustable lock rod, double-end switch bar, 
detector bar connection, circuit controller and conduit con- 



114 



RAILWAY SIGNALING 




-^ p; 




ELECTRIC INTERLOCKING 



115 



nection to trunldng. It operates very much like the Model 4 
machine, but it is somewhat smaller and more compact. . 

70. Semi-automatic Signal Control. — In Fig. 128, when the 
signal lever is reversed, a battery circuit is set up from the plus 
bus bar through the reverse controller contact, the control wire, the 
signal motor operating field and armature, and main common. 
The first 40 degrees of the mechanism movement does not change 
the position of the signal arm, but puts under tension a set of 
coil springs which are strong enough to rotate the motor on the 




Fig. 126. — Pole changer for Model 4 switch machine. 
Tripper arm N shown at the top of its vertical movement. 

return movement with sufficient speed to generate the current 
for energizing the indication magnet on the lever. If the track 
circuit be occupied, the mechanism is held in the zero position 
against the tension of the springs by the opening of contact 
Bi and the closing of contact Ai which connects the holding 
field in series with the operating field and armature of the signal 
motor. If the track circuit be not occupied, the mechanism wdll 
not stop in the zero position, but will continue its movement, 
taking current through the track relay armature contact and 
circuit breaker B2, and bringing the signal blade to the proceed 
position. Just before it reaches this position, contact B2 opens 



116 



RAILWAY SIGNALING 




il 



ii 



ELECTRIC IXTERLOCKIXG 



11 



and A 2 closes, again cutting the holding field in series with the 
operating field, thereby retaining the signal mechanism and signal 
arm in the proceed position. 



3 



I 






2-0 



ho3 



If a train enters the 
track section controlling 
the signal, the track relay 
becomes deenergized and 
its relay armature drops 
breaking the circuit and 
allowing the blade to re- 
turn to the zero position. 
This movement of the 
blade causes the armature 
of the motor to run in the 
opposite direction making 
it act as a "snubber" to 
check the momentum of 
the blade. Circuit breaker 
contact Ai closes, thereby 
retaining the mechanism 
in the zero position during 
such time as its lever may 
be reversed. The signal 
arm cannot again be cleared 
until the mechanism is re- 
turned to its — 40-degree 
position. When the lever 
is restored normal, energy 
is cut off from the motor, 
and the mechanism is re- 
turned to the —40-degree 
position by the tension of 
the coil springs. Just be- 
fore the blade reaches this 
position, contact Bi closes, 
thereby connecting the 

motor armature and operating field in their original closed 
circuit, which includes the indication magnet. The backward 
motion of the motor generates enough current to energize the 
indication magnet and to allow the lever to go to its normal 
position. If the controlling lever be placed normal before a 




118 



RAILWAY SIGNALING 




train enters the track section, the signal arm returns to the 
stop position and the mechanism continues to run backwards 

until it reaches its —40- 
degree position, generating 
current to give the indica- 
tion as before. 

71. Dwarf Signals.— 
Some dwarf signals are 
operated by means of 
solenoids. There are two 
sets of coils, a low-resist- 
ance operating coil and a 
high-resistance holding coil. 
The plungers of the solen- 
oids are connected directly 
to the arm of the signal. 
As there is no means for 
getting dynamic indica- 
tions, an indication wire 
in addition to the control 
wire is necessary. In Fig. 
129, as soon as the signal 
lever is reversed as far as 
it will go, the battery cir- 
cuit is set up from the plus 
bus bar through the lever 
controller contacts in re- 
verse position and through 
the polarized relay to the 
operating coils A-A. This 
brings the signal arm to 
the proceed position. Just 
as the arm reaches this 
postion, circuit breaker C 
is opened causing the cur- 
rent to flow through the 
holding coils B-B in series with the operating coils A-A , retaining 
the arm in that position. No indication is given for this position. 
The coils B-B are high-resistance coils in order to reduce the 
current as much as possible. When the signal lever is returned 
towards normal as far as it will go, the battery circuit is broken to 



a) 

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i! 



ELECTRIC INTERLOCKING 



119 



the solenoid. The coil spring which was placed under compres- 
sion when the signal was cleared now causes the arm to return to 
the horizontal position. Its first movement closes contact C and 
its final movement closes contact D. This permits battery 
current to flow through the indication wire and release the signal 
lever for final movement to normal. By observing Fig. 129, it is 
seen that in its final normal position, the indication circuit is 
broken in order to eliminate a waste of current. In Fig. 130 is a 
sketch of the Model 2 solenoid dwarf signal operating mechanism. 




Fig. 130. — Model 2 solenoid dwarf signal operating mechanism. 



.-1 1-^4 2 Operating Coils 
Bi-Bz Holding Coils 
C Operating Contact 

D Indicating Contact 

E1-E2 Solenoid Plungers 



Yoke 
Rack 
Pinion 
Crank 



The two sets of coils A i-A 2 and B1-B2 operate the plungers Ei-E2> 
Motion is transmitted to the signal arm by means of the yoke F, 
rack Gy pinion H, and crank J. The contact springs C and D are 
operated by a commutator on the same shaft as pinion H. Con- 
tacts C and D are both broken when the signal arm is clear. D 
is closed only when the arm is horizontal in order to give the 
indication. 

72. Cross Protection. — When all functions are at rest they 
are on a closed circuit. In order to eliminate the possibility of 
foreign currents operating a function, one polarized relay of low 
resistance is placed in the plant for each lever on the machine. 



120 



RAILWAY SIGNALING 



It may be fastened to the terminal board on the back side of the 
machine or it may be mounted on top of the machine as shown 
in Fig. 131. It is placed in the indication circuit and is so con- 




FiG. 131 . — Model 2 unit lever type interlocking machine. Collin wood Interlock- 
ing Plant, L. S. & M. S. R'y- 

nected that all currents giving indication must pass through the 
polarized relay in such a direction as will keep its contact closed, 
while all unauthorized current, such as would come from short- 

CiRcuiT Brelaker A 



^ 



Energized Control ffiRti • 



110 VOLT 2=: 

BATTtRY -=- 



M 



POLARiZE-D Relay 



ruNCTIOIi AT REST 
FUMCTION BEING OPERATEIO 




Fig. 132. — Simplified circuit showing the principles of the G. R. S. cross protec- 
tion system. 

circuits or from foreign circuits, must flow in the opposite direc- 
tion. This causes the relay to break its contact and shut off the 
current to the whole plant. In Fig. 132 is a simplified circuit 
showing the principle of this system of cross protection. Func- 



ELECTRIC INTERLOCKING 



121 



tion C is at rest. The current through B normally flows in the 
direction indicated by the heavy arrow. If there should be a 
short-circuit, as at X, while the function D is being operated, the 
current would travel through B in the opposite direction, as 
indicated by the dotted arrow, reverse its polarity and break 
contact through the circuit breaker A. This, in turn, would 
release its armature and break the circuit to the whole plant. 
Figure 133 is a more comprehensive sketch showing wiring for a 
switch and signal. 



'C.isa)iT~6Rt/uvER """1 



lflTt(«l.OCRin& MACHinC 



.m 




FiQ. 133. — Circuits for operating switchboard, interlocking machine and switch 
and signal functions. 



73. Alternating-current Interlocking. — In the case of alternat- 
ing-current interlocking the switches and signals are operated 
directly from a 110- volt circuit, 25 or 60 cycles. The switches 
are operated as in the direct-current system and give a dynamic 
indication. The semaphore type of signals, however, is not 
equipped for dynamic indication. Indication is given by energy 
through a contact on the signal circuit breaker, which is closed 
when the signal is in the stop position. When the light type 
of signals is used with the alternating-current or direct-current 
systems, indication is given through a back contact on the con- 
trolling relay. 

The use of alternating-current interlocking is not advisable 
unless two reliable sources of alternating-current power are 
available, and then its use is questionable unless a failure of the 



122 



RAILWAY SIGNALING 



source of signal power also takes away the motive power of the 
cars or trains, as is sometimes the case on electric railways. 

74. Illuminated Track Diagram. — One of the features of a 
power interlocking plant is a track indicator, which is a miniature 
yard layout, placed above the interlocking machine in the tower 
to aid the towerman in following the movements of the trains. 
One such type of indicator is the illuminated track diagram in 
which the tracks, switches and signals are painted on a ground 



>■. 






'■: jBsK^^^^^mi 



Fig. 134. — Illuminated diagram. 



glass set directly above the interlocking machine, where it is 
plainly visible to the towerman. Very small incandescent lamps 
controlled by the track circuits are placed along each track behind 
the glass. Two colors of lamps are used alternately, red and 
white. When the track is not occupied, the white light burns 
and when it is occupied the red light burns. This furnishes the 
means for a signalman to follow easily the movements of every 
train through the yard, even though he cannot see the yard itself. 
Figure 115 shows such a diagram in the Chicago Terminal of the 



ELECTRIC INTERLOCKING 



123 



Chicago and North Western Railway. A newer type of illu- 
minated diagram is shown in Fig. 134. The miniature lamps 
on the face of the diagram are each connected to a track circuit. 
The current for illumination is taken through the relay points in 
that section or through a repeater relay located in the tower. 
The lamp may be normally lighted when the track circuit is 



CABINET -1 STICK PUSH BUTTON 




Fig. 135. — Electro-mechanical interlocking machine. 



not occupied, in which case the light goes out as the train occupies 
that section. The more general way is to have the lamp illumi- 
nated only during the time the train is in the track circuit. 

75. Electro -mechanical Interlocking Machine. — The electro- 
mechanical interlocking machine is a combination of electric and 
mechanical interlocking equipment. The large mechanical levers 
operate switches and derails, while the electric levers control 
signal, electric locking and indication circuits. The mechanical 



124 RAILWAY SIGNALING 

levers are spaced 5 in. apart, while the electric levers are spaced 
23-^ in. apart. Those electric levers mounted in the same vertical 
plane as the mechanical are used for giving indications of the 
movements of switches or derails, and the others for controlling 
the signal circuits. 

The mechanical locking is the vertical type, operated in the 
same manner as in the electric machine. The rotary controllers 
on the back of the machine operate around a vertical axis. They 
are made in five tiers with six contacts in each, making thirty 
contacts for each circuit controller. This arrangement of levers 
and locking provides for detector locking and for switch and signal 
indications. It permits a much smaller plant than would be 
required if all the levers should be of the mechanical type, and 
allows an extension of a plant without enlarging the tower for lever 

space. J 

i 

UNION SWITCH AND SIGNAL COMPANY TYPE "F" SYSTEM j 

76. General. — This system of electric interlocking differs from 
all other existing systems of electric interlocking in that the actual 
power for operating the switch and signal mechanisms is drawn 
from a pair of busses or mains which extend throughout the in- 
terlocking plant so as to supply each function when required. 
In all other systems of electric interlocking the power which 
operates any function is fed to that function over a separate wire 
or set of wires from the interlocking machine. 

77. Power Supply. — The usual source of power supply for the j 
Type ''F" interlocking plants is a set of storage cells, charged ) 
from local generators or mercury arc rectifiers. However, a 
number of Type ^'F" plants employ alternating current ex- 
clusively, in which case provision is made for taking this power 

from any one of two or three different power lines in order to 
provide a constant supply of power in the event of failure of any 
of the lines. In some installations devices are provided to change 
the connections automatically in case of failure of power on the 
line being used. One hundred and ten volts is the usual potential 
employed on the plant, whether alternating current or direct 
current. 

78. Interlocking Machine. — This system is so similar to 
the electro-pneumatic system that the same interlocking machine, 
with slight modifications, is used. Operating on a higher voltage, 
the indication magnets for direct current are wound to about 



ELECTRIC INTERLOCKING 



125 



2,000 ohms resistance. The contact arrangement for switch 
control is changed sUghtly; otherwise, the machine is just as 
described for the electro-pneumatic system. 

79. Power Mains. — The power mains consist of a pair of 
relatively heavy wires extending throughout the plant with taps 
at each switch and signal, not unlike an electric light circuit. 
These power mains correspond to the compressed air line in the 
electro-pneumatic system. They do not have to be heavy 
enough to carry current for operating all the functions at the 
same time. Since the mechanical interlocking feature prevents 
the operation of many of the functions at one time, the mains 



QUICK SWITCH CONTACTS 
INDICATION RELAY 



CONTACTS FOR 
S.SVSIGNAL 
CONTROL 




(^ 

?/^ 



pnm 



^ 



^ 






lETECTOR 
CIRCUIT 
RELAY 



•switch 1 

CIRCUIT 
CONTROLLER) 



ICOMPENSATING FIELD 



-MAIN FUSE 



•SO 



^t1' 



3 



JuuJ 
nnnr 



..C.BUS MAINS -<^ 



Fig. 136. — Complete operating and indication circuits for a single switch. 



need to be only heavy enough to supply current to those that 
can be simultaneously operated. 

At each switch movement is a controller connected to the com- 
bination board on the interlocking machine by a pair of small 
electric wires. These controllers correspond to the switch valves 
in an electro-pneumatic plant and govern the flow of current from 
the power mains to the switch motors. The switch circuit con- 
troller operates on the polarized principle and responds to rever- 
sals of polarity in the control wires by changing its contacts. 
Springs and bands on the switch lever roller in the interlocking 
machine are arranged as a pole changer. When the switch lever 
is reversed, the polarity of the controlling current is reversed, the 
controller contacts change and the switch motor operates. In this 
system the control wires do not carry the current that actually 



126 



RAILWAY SIGNALING 



runs the switch motor; the switch circuit controller is a high- 
resistance instrument and the control wires may be as small as 
mechanical strength will allow. It is customary to use No. 16 
copper wire and to group them into cables for protection against 
mechanical injury. This reduces the amount of copper necessary 
in the plant, especially where the switches are located at a con- 
siderable distance from the tower. 

The switch circuit controller used with 110-volt direct-current 
control, shown in Fig. 137, is called the '^ normally deenergized'* 
controller because it automatically locks itself in place and 
then cuts off its controlling current. It contains a neutral 



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Fig. 137. — Switch circuit controller, direct current, normally deenergized type. 



magnet of two coils, and a polarized magnet of three coils. The 
neutral magnet is energized by a reversal of the polarity in the 
control wires, current flowing from one of the control wires 
through the coils to the power main of opposite polarity. 

When the neutral armature picks up, its contacts open the 
switch motor circuit and close the circuits to the polarized 
magnet. One coil of the polarized magnet then receives current 
of a definite polarity and from the power mains; the other two 
coils of the polarized magnet receive current from the two control 
wires. When the polarity of these wires has been reversed, the 



ELECTRIC INTERLOCKING 127 

polarized armature reverses. The polarized armature carries 
contacts which change the circuit for the neutral magnet from one 
of the power mains to the other. Thus the neutral magnet be- 
comes deenergized, and its armature is released, mechanically 
locking the polarized armature in place. Its contacts open the 
two circuits to the polarized magnet, and close the switch 
motor circuits to throw the switch. All the magnets of the 
controller are thus deenergized until the next reversal of the 
polarity of the control wires by the switch lever. 

This controller also contains an overload circuit breaker. 
Should the switch points be obstructed, the switch motor would 
be overloaded and the breaker would open as any circuit breaker 
would. It is so arranged, however, that it is reset by the neutral 
armature when the switch lever is moved to the other indicating 
position. Thus the switch motor is protected without the use of 
fuses which require replacement; and the operator can move the 
switch back and forth in an effort to dislodge or crush the obstruc- 
tion. A separate set of contacts on the switch movement 
opens the motor circuit when the switch has been thrown and 
locked. Figure 136 shows the complete operating and indication 
circuits for alternating current to operate a single switch. 

The control of signals in the Type *'F" system is accomplished 
very much as it is done in the electro-pneumatic system, except 
that an electrical device must replace the air valve. Two small 
wires connect the signal lever with a relay or its equivalent at the 
signal. That relay when picked up closes the signal motor cir- 
cuit from the power mains. When the signal lever is restored 
to its normal indicating position, it breaks the connection to the 
control wires, the relay drops and the signal falls to the stop 
position by gravity. 

80. The Indicating System. — The indicating system is es- 
sentially the same as that described for the electro-pneimiatic 
system with only such changes as are necessitated by the differ- 
ence in voltage. Obviously, the indicating system which is 
independent of the control system may be of a different voltage, 
may be operated from a different source of power, or may 
be alternating current when the control system is direct current. 
Each switch movement embodies a pole-changing indication cir- 
cuit controller that controls a polarized relay in the tower. Each 
signal when in the stop position completes a circuit for its 
indication just the same as in the electro-pneumatic system. 



128 



RAILWAY SIGNALING 



81. Style "M" Switch Movement.— Figure 139 shows a Style 
"M" switch and lock movement used for throwing switches and 
derails. It consists essentially of motor, clutch, reduction gears, 
mechanical movement arranged to operate in the usual order to 
unlock, throw and lock a switch, and circuit controller that does 
the double duty of opening the motor circuit after the switch is 
thrown and locked, and of controlling the indication circuit. 
The purpose of the clutch is to absorb shocks due to the momen- 
tum stored up in the rotating armature, and to limit the load that 
may be imposed upon the motor by an obstructed switch. 




Fig. 138. — Style "M" switch layout. 

(B) illustrates the normal positions of the immediate parts 
instrumental in throwing and locking the switch points. Start- 
ing from this position a reverse movement is begun by the 
clockwise rotation of combined shaft and crank arm X. Lug 
x' on the top of crank X acting against roller z' on motion plate 
Z, effects the unlocking of the switch points. Meanwhile, roller 
X on the underside of crank X has moved through an arc of 40 
degrees in groove y in switch operating bar Y, thus freeing 
the bar for the reverse stroke. During the next 140-degree 
revolution of crank X, roller x engages the reverse operating 
face of groove y and throws switch operating bar Y to the reverse 
position. 



ELECTRIC IXTERLOCKING 



120 



(C) shows the relative mid-stroke positions of the switch 
operating bar Y and lock bar Z; the crank X is still rotating 
clock-wise; but is not transmitting motion to the lock bar, as 




{A) Switch and lock movement assembled. 



o o : 
o o 




) 



jmsrav 



(B) Diagram of driving parts in normal position. 




^ •"^■' /Ul^^^ ''^ 



/msmT-x^ 



(C) Diagram of driving parts in middle (D) Diagram of driving parts in reverse 

position. position. 

Fig. 139. — Stvle "M" switch and lock movement. 



lug x' has become disengaged from roller c' and the arcs of contact 
at V and f' between the crank X and lock bar Z are radial to the 
center of the crank shaft. 



130 



RAILWAY SIGNALING 



The complete reverse position is shown in (D). Roller x on 
crank X acting in groove y has pulled operating bar Y in and 



. q 1 


■^^^ 


P 


fC^i 


HM^'^^^^^C ^^1 


UM 


Q I wm fW 


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Ll 


m^^^^mM 


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'It 


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^J^^H^^^^^OmH 


HBfe| 


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1 



Style "M" lock box and inverted view of circuit controller. 




Style " M " circuit controller with point detector. 
Fig. 140. — Style " M " indication circuit controller. 

secured it; lug x"^ has come into contact with roller z, thus driving 
locking bar Z to the full reverse position. 



ELECTRIC INTERLOCKING 131 

Starting from the normal position of the main crank, which 
is 20 degrees beyond dead center, the consecutive events and 
respective angular positions of the crank are as follows: 

Degrees 

Normal position. 

5 Indication supply opened and relay shunted. 

10 Normal motor circuit closed. 

15 Detector bar even with top of rail. 

20 Dead center. 

40 Points unlocked. 

40 180 Degrees — Throwing switch points. 

200 (Dead center) points locked full width of lock bar. 

210 Reverse motor circuit opened. 

215 Shunt removed and indication circuit completed. 

220 Reverse position. 

82. "SS" Control. — In this system, as in the electro-pneumatic 
system, it is customary to operate more than one switch, for 
example, the two switches of a crossover, from one switch lever, 
and to control several signals governing converging or diverging 
routes from one signal lever; also it is customary to employ the 
''L" position of a signal lever for one signal or group governing 
train movements in a corresponding direction on the track, and 
the "R" position for train movements in the opposite direction 
over the same track. The ability to accomplish this multiple 
control makes it possible to employ a comparatively small 
machine for a large number of switches and signals. Where 
several tracks lead onto a common track, and each of these 
tracks has its own signal, these signals may all be controlled by 
one signal lever. The circuits for these signals, however, must 
be arranged so that only the proper signal will clear. This is 
known as the selective control of converging signals. In con- 
sidering the control of several signals from one lever it must be 
remembered that each signal governs a definite route over 
switches and derails set a definite way. Each switch or crossover 
controls a corresponding polarized relay in the tower, as previ- 
ously described. Each relay must correspond in the position of 
its polarized armature with the controlling lever in order that 
the indication be received. Therefore, each switch must have 
been setting in accordance with its lever when the indication 
was received. The control wire for a given signal is not only 
controlled by its signal lever, but is also carried over neutral 
and polar contacts on the indication or ^'SS" relays, and over 



132 



RAILWAY SIGNALING 



contacts on the levers of all switches and derails in the route 
governed by that signal; and these contacts are arranged so 
that the}^ are closed only when all the relays and levers are 
properly set for movement over that route. Thus, when a 




Fig. 141. — Track and signal layout. Alternating current used in interlocking. 

signal is cleared, a check is provided that the switches are properly 
set, that the switches correspond with their levers, and that no 
switch is manually operated or even unlocked after the indication 
is received. The route to be properly set for one signal must be 

Switch Indicating anci Signal Contnyl Rebys 




Mechanical Stick Push Bufton 
for "Calling On"arm control 



0-^ 



Fig. 142. — Signal control circuits for Fig. 141. 

wrong for all others; hence all the other signal control wires must 
be open at certain lever contacts and relay contacts, preventing 
all other signals from clearing. This method of controlhng 
signal circuits through switch lever contacts and relays is known 



ELECTRIC JNTERLOCKING 133 

as ''SS" control. A sample track layout and the corresponding; 
signal control circuit are shown on Figs. 141 and 142. Its 
advantages lie in the high degree of safet}'- accomplished and in 
avoiding the interruption of the signal control wires at the 
switches with the possibilities of crosses and grounds. Each 
signal control wire runs direct from the tower to the signal. 

83. Auxiliary Features. — In connection with the semi- 
automatic control of signals, the push button, a device sometimes 
used with the signal levers, as shown in Fig. 98, should be mention- 
ed. Its purpose is to close the circuit for a calling-on arm when 
conditions such as an occupied track circuit prevent clearing the 
semi-automatic arms of a signal. After the signal lever is 
reversed, the button is pushed in, carrying with it a vertical pin 
that closes the contacts below and engages with a hole in the 
spring above, retaining it in the pushed-in position. When the 
signal lever is restored to its normal position, the lever latch 
raises a cam which, in turn, raises the spring out of engagement 
with the pin and allows the button to snap out into normal 
position. 

The interlocking machine is designed to mount a row of lever 
lights when desired. These lights indicate by being illuminated 
or dark, which switches may be operated and which signals may 
be cleared. 

84. Union "S-7" and "S-8" Electro -mechanical Interlocking 
Machines. — The Union ''S-7" electro-mechanical interlocking 
machine consists of a standard Saxby and Farmer mechanical 
machine above the locking bed of which is a frame supporting 
one or more electric lever units, as shown in Fig. 143. The 
electric lever units are spaced five inches from center to center, 
the same as the mechanical levers; and the number of electric 
lever units may be equal to, but no greater than, the number of 
mechanical levers and spaces. 

Each electric lever moves forward and back through a total 
angle of 60°, and by means of bevel gears rotates a horizontal 
shaft which carries the segment for the single lock magnet, and an 
insulating roller with contact bands very similar to that in an 
electro-pneumatic machine. This shaft also carries a crank to 
which is attached the vertical rod extending down to the locking 
bed, described in the following paragraph. 

The mechanical locking between all of the levers, mechanical 
and electric, is accomplished in the regular Saxby and Farmer 



134 



RAILWAY SIGNALING 



locking bed. Electric levers are connected to the locking bed by 
adjustable vertical connecting rods which extend through the 
locking bed and operate loose sleeve driving pieces. These 
driving pieces rotate on spht journals clamped to the locking 
shafts of mechanical levers, thus permitting an electric lever to 
drive its locking bar without interfering with the operation of the 
locking shaft which supports the driving piece. The driving 
pieces are made in various lengths so that a selection of locking 
bars may be available, 

It will be noted that a longitudinal locking bar is required for 
each electric lever as well as for each mechanical lever, thus 
necessitating a wider locking bed than would be required for the 
mechanical levers alone. 



Jl 


Ifi 



Fig. 143.— "S-7" Elec- 
tro-mechanical interlock- 
ing machine. 



Fig. 144.— "P-5" Elec- 
tro-mechanical interlock- 
ing machine. 



The ''S-8" interlocking machine is a modification of the 
"S-7" machine and may have as many as three lock magnets on 
each electric lever. It may also have its contact rollers arranged 
vertically below the electric units, where more space will permit 
a greater number of contacts. Either machine may be equipped 
with quick switch, lever indicator lights, latch contacts, or stick 
push button, thus incorporating practically aU of the features of 
the electro-pneumatic or Type "F'^ machines. 

The *'S-7" and "S-8" machines find their apphcation at 
mechanical interlocking plants where some of the functions are 
electric, such as signals, or remote switches, or where it is desired 
to employ electric detector locking, route locking, check locking 
between towers, or electric indication of mechanical switches. 



ELECTRIC INTERLOCKING 135 

In many cases the electric units are added to an existing Saxby 
and Farmer machine, where the plant is being enlarged by adding 
switches and signals; in such cases existing mechanical signals can 
be converted to electric, operated by the electric levers, thus 
making the former signal levers available for switches. The 
number of operated functions can thus be materially increased 
without adding to the length of the mechanical machine, which 
would not infrequently require enlargement of the interlocking 
tower. 

85. Union "P-5" Electro -mechanical Machine. — Another 
development in electro-mechanical interlocking machines is 
represented by the Union ''P-5" machine, one of which is shown 
in Fig. 144. This machine is made by combining the frame and 
levers of a Saxby and Farmer machine, with the electric levers, 
locks, spring combination board, and locking bed of a Type "F'* 
electric machine. In this arrangement each mechanical lever is 
locked full normal or full reverse by the corresponding electric 
lever directly above it, by means of horizontal locking bars and 
vertical tappets connected respectively to the rocker-links of the 
mechanical levers and to cranks on the electric levers. In order 
to reverse a mechanical lever, the electric lever is first moved to 
the center position, thus unlocking the mechanical lever, which 
can then be reversed; finally, the electric lever is moved to full 
reverse, thus locking the mechanical lever in the reversed position. 

The locking of mechanical levers by electric levers provides for 
detector locking and electric indication of mechanically operated 
switches the same as if the switches were power operated. Elec- 
tric levers are interlocked the same as in the Type ^'F" machine. 
Mechanical levers are not interlocked except through their 
respective electric levers. The electric levers are spaced 23^^" 
between centers, and the mechanical levers b") the intermediate 
or alternate electric levers which do not come directly above 
mechanical levers are used for strictly electrical purposes, such as 
the control of signals. 

FEDERAL SIGNAL COMPANY SYSTEM 

86. Interlocking Machine. — The Federal interlocking machine 
is built with short levers and with quadrants and rocker-links 
similar to those in the Saxby and Farmer mechanical plant. 
The machine is made in sections of eight levers, spaced 3 in. 
center to center. It has a horizontal locking bed of miniature 



136 



RAILWAY SIGNALING 



Style A type placed directly behind the levers, and this may 
be enlarged to suit requirements in proportion to the number of 
levers grouped in a machine by adding plates to increase the 
depth of the locking bed. Figure 146 shows a section of a 
two-plate machine. The latch block roller travels in the rocker- 
link slot when the lever is moved from the normal to the reverse 
position, and the lifting of the lever latch operates the rocker- 
link just as previously described in the mechanical plant. 

The tappet bars are connected to the rocker-link by a tappet 
link. On the extreme outer end of the tappet is a driver that 
operates the contact button shaft of an auxiliary circuit controller. 




Fig. 145. — Federal interlocking machine. 

This controller furnishes a means whereby electric checking of 
the position of each lever in the machine becomes feasible. On 
the front of the machine is another vertical controller connected 
by a rod to the tail of the lever. This controller moves simul- 
taneously with the lever itself. The auxiliary controller in the 
back moves simultaneously with the lever latch and hence 
becomes a factor in the lever locking. 

The front circuit controller is provided with a rod having 
three- bearings. Between the top bearing and the intermediate 
one is a double pole, double throw, heel and toe type of knife 
switch. This switch is operated by the roller on the controller 
rod and functions to make and break circuits to the switch and 
signal mechanisms. Between the intermediate bearing and the 



i 



ELECTRIC INTERLOCKING 



137 



bottom one are located insulated contact buttons which are 
adjustable on the controller rod in relation to the fixed contact 
springs, so that the contact may be timed to make and break 
with desired positions of the controller rod and thus control 
auxiliary circuits as may be required by different conditions of the 
interlocking plant. These contacts are in general used for the 
control of route locking circuits wherever these may be employed. 




DK DJ 



Fig. 146. — Section through Federal interlocking machine. 



Each lever may also be equipped with an electric lock mounted 
directly above the tappet bars and immediately behind the levers. 
These locks are of the solenoid t3'pe and are wound to a resistance 
of 8 ohms. They are arranged to check or hold the movement of 
the latch by means of notching a plate on the tappet in various 
portions of the cycle of operation. The most common cuttings 
for the electric lock are the "normal and reverse" and the "half 
reverse." When the lock is cut "normal and reverse," a notch 
is provided in the plate riveted to the tappet wherein the solenoid 



138 RAILWAY SIGNALING 

plunger may drop and prevent the lifting of the latch from the 
normal or reverse position of the lever except when the lock has 
been preliminarily energized and the solenoid core lifted from 
the notch in the locking plate attached to the tappet. When the 
lock is cut ''half reverse," the notch is so situated that the lever 
may be returned to its normal position, but the latch will be 
prevented from dropping unless the lock has been energized and 
the conditions requisite to the placing of the latch normal have 
been fulfilled. The half reverse cutting is generally found on 
signal levers. 

Each lock is provided with an auxiliary contact that holds 
the circuit to the coil open until it is desired to move the lever 
to which the lock is attached. This effects the saving of elec- 
tricity inasmuch as the circuits are closed only when it is desired 
to use them. The levers are provided either with or without 
lights as may be desired. The light, however, furnishes a 
ready means of indicating the condition of the track over which 
a switch lever might govern; and in general, the light will when 
illuminated, indicate that conditions are right for the energiza- 
tion of the electric lock. 

87. Type 41 Switch Machine. — The Type 41 switch machine is 
adapted for circuits of 100- volt and 20- volt potential direct 
current as well as for circuits of varying potential and frequency 
when provided with suitable alternating current motors. Figure 
147 shows an assembly and part section of the switch machine. 
The motor, in the case of the direct-current operation is of bipolar 
construction. Each field pole is furnished with two field windings, 
one for each direction of rotation. Since the control of the motor 
is effected by means of three wires, one for reverse operation and 
the other for normal operation, the double sets of field coils 
furnish a means of reversing the direction of rotation by merely 
energizing one or the other of the two control wires in combina- 
tion with the common or return which is connected to one of the j 
brushes. The other brush is connected to a point common to ( 
both field windings. 

By means of a train of gears the motor drives a main cam gear, 
GP, which, in turn, drives the circuit controller rods KB and 
the connecting rod FV attached to the stud HB. Through the 
medium of this stud HB, the rotary motion is changed to a 
reciprocating one. The rod FV operates the locking plunger FX. 
The escapement cam, pivoted on stud GY, is provided with a stud 



ELECTRIC INTERLOCKING 



139 



HA that engages operating connections KK so that when stud 
HA is rotated around GY , KK will be given a motion transverse 
to the mechanism case, and being connected to the switch points 
will move them from one position to the other. The escapement 
cam FT is provided with cam surfaces machined to be concentric 
with the main stud GZ in the extreme positions of the operating 
connections KK; therefore, when rotation of the main gear GP 
takes place, no movement of cam FT occurs until the operating 




Fig. 147. — Type 41 switch machine. 

stud HB reaches a position where it engages the end of the con- 
centric cam surface opposite stud HA from the center stud GY. 
This movement of HB engages connecting rod FV, however, put- 
ting it in operation and moving it towards the right-hand end of 
the mechanism case. Such movement withdraws lock plunger 
FX from notches cut in the lock rod KL and thus unlocks the 
switch points. Continued rotation of HB around the center 
GZ moves the escapement cam FT to a position opposite to the 
one shown in the figure, while the second concentric cam surface 



140 RAILWAY SIGNALING 

goes to a position concentric with the stud GZ. The operating 
connection KK and the lock rod KL move to their reverse posi- 
tions from that shown in the figure and another locking notch in 
KL comes to register with the locking plunger FX. Still further 
rotation of stud HB puts the operating rod FV in tension drawing 
it forward and thereby plunging the lock rod in its reverse position 
from that shown in the figure. 

After the lock plunger has entered through the lock rod, con- 
tinued rotation of the gear GP causes the cam surface provided on 
its top to engage the roller studs on the lower sides of controller 
operating rods KB and shifts the insulated contact buttons from 
engagement with the contact springs and thus disconnects the 
motor from the operating circuits. The connecting rod FV 
stands at an angle to the center line of the switch mechanism in 
both the normal and reverse positions. This change in angular 
position occurs simultaneously and coincident with the movement 
of the switch points, thus enabling the selection of an indication 
contact to the right or the left of the center line closed only when 
the lock plunger advances towards the motor a sufficient distance 
to insure its passage through the proper notch provided in the 
lock rod. 

Sixty two revolutions of the motor are required to throw the 
switch. The first 16 are necessary to move the detector bar 
and unlock the switch. The next 30 throw the switch; and the 
last 16 lock the switch and throw the detector bar again. The 
last revolution of the motor disconnects it from the operating 
circuit. 

In order to prevent the mechanism from damage when it meets 
a serious obstruction in the switch points, a friction clutch is 
provided in the transmission between the motor and the main 
gear. The rotation of this clutch, GR, is caused by the rotation 
of gear GN due to the friction of their engaging surfaces. 

A dynamic brake is used to control the operation of the switch 
mechanism between its final normal and reverse positions and 
also to control the apphcation of the dynamic braking or regenera- 
tive circuit required at the end of each switch operation in order 
to prevent shock or damage due to the sudden stopping of the parts 
at their extreme positions of operation. This device is used also 
to control the excitation of the indication transformers. It is a 
compact electro-magnet device comprising two coils and a swing- 
ing armature. The armature is used to close contacts in accord- 



ELECTRIC INTERLOCKING 



141 



ance with its attraction to the right or left, and this, in turn, is 
controlled by the energizing of the right- or left-hand windings. 
88. Switch Machine Control and Indication Circuits. — The 
following description of the switch machine control and indica- 
tion circuits is taken from the January, 1920, issue of the Railway 
Signal Engineer.^ 

"The control and indication of the switches is illustrated by the 
tj^pical circuit shown in the diagram. When a lever is operated to 
move a switch, direct current flows through the double-pole double- 
throw switch actuated by the movement of the lever, and then over 
either the normal or reverse control wire (depending on the position of the 
lever), then through the circuit controller in the switch machine, and one 
of the coils of the circuit controller known as the 'dynamic breaker,' 
which is housed in the switch machine. During the initial movement 
of the switch machine and while the dynamic breaker is energized there 
is a bi-circuit set up through which direct current is supplied to the 
motor of the switch machine. 



Lei/er Normal 



Trans^ormei 




X. To Breaher 

Supply 

Fig. 148. — Typical control circuit diagram for switch. {Railway Signal 

Engineer.) 

''When the operation of throwing and locking up the switch has been 
completed, alternating current is transmitted over the main direct- 
current common wire and the alternating-current indication- common 
wire. Each section of the plant has a branch of these two common 
wires. The alternating current transmitted over these two common wires 
is stepped up to 220 volts when it reaches the indication transformer 
located in the switch machine. This secondary current, at 220 volts, 
is transmitted to the 'safety and indication magnet' on the lever 
controlling the function, over the idle control wire and the main direct- 
current common, which releases the lever so it maj^ be placed in either 
the full normal or full reverse position, depending on the position of the 
function. The coils on the dynamic breaker located in the switch 
machine housing are of the slow releasing type, and hold the controller in 

^ Page 61. Electric Interlocking at Winchester, Ky., by F. H. Bagley. 



142 



RAILWAY SIGNALING 



the energized position for a sufficient length of time after the direct 
current which operated the mechanism has discontinued to allow the 
alternating indication current to perform its function. 

"The 'safety and indication magnet,' referred to in the previous 
paragraph and shown in the illustration, is equipped with an armature 
at each end and automatically selects or attracts either one or the other 
of these armatures, depending upon whether alternating or direct 
current is passing through the magnet coils. This is accomplished as 
follows : 

''With the alternating current scheme of indication, the magnetic 
lines of force will be set up through the path indicated by the dotted 
line, since the copper ferrules A, B, and C will effectively choke the 



/nd/cafion Fftjn$eh 




\Co/'/s In Mu/Hp/e fbrSgnaf Let/ers 
Colls 1/7 Series forSwUch Levers 



Fig. 149. — The safety and indication magnet. {Railway Signal Engineer.) 



magnetic field, set up by the alternating current, from going through 
that part of the iron core enclosed by them. This will cause armature 
G to be attracted, which delivers the indication. The iron path F is 
of small cross-section and consequently high reluctance, forming part 
of the magnetic path for the magnetic flux set up by the alternating 
current. If a direct current is caused to flow through the indication 
magnet, the indication mechanism will not be operated by this direct 
current, since the magnetic lines of force will then take the path shown 
by the arrows, because the copper ferrules 2ii A, B and C have no 
choking effect on the magnetic flux set up by a direct current. The 
path F carries part of this magnetic flux, but on account of the great 
reluctance of path F it cannot carry all of this flux so that part flows 
around through armature D. Armature G is not attracted, since the 
large cross-section of E provides ample path for the magnetic flux. 
Armature D is attracted, which opens the circuit energizing the main 
circuit breaker on the operating switchboard, causing this circuit 
breaker to release and thereby cutting power from the section of the 
plant affected. 



ELECTRIC INTERLOCKING 



143 



*'It is evident that if direct-current energy should by some chance be 
appHed to the idle control wire, it might have a tendency to cause the 
switch mechanism to assume an opposite position to the control lever. 
Since the idle control wire forms a part of the indication circuit, and 
the safety and indication magnet is connected at all times between the 
idle control wire and common, a portion of any direct-current energy 
applied to the idle control wire will flow through the safety and indica- 
tion magnet, attracting the armature that opens the cross protection 
circuit, and thus causing the main circuit breaker in that section of the 
plant to open. This provides an effective means of cross protection. 




Fig. 150. — Hall interlocking machine. 

"This indication mechanism is applied in exactly the same form to 
interlocking machines equipped for alternating-current control, direct- 
current indication, by merely turning the iron core around. Then 
armature D is attracted by the magnetic flux set up by the direct- 
current indication. Armature G then becomes the cross protection 
armature, being energized when the indication wires are crossed with 
the control wires carrying alternating current, and opening the main 
cross protection circuit." 

89. Federal Electro -mechanical Interlocking Machine. — A row 

of miniature levers similar to those on the electric machine is 
located above the mechanical levers and is provided with the 
same spacing. Mechanical locking between both sets of levers 
is accomplished in the vertical locking bed placed just behind the 



144 



RAILWAY SIGNALING 



mechanical levers. Circuit controllers can be applied to the 
rear of the machine and operated by either the mechanical or 
electric levers. 

HALL SWITCH AND SIGNAL COMPANY SYSTEM 

90. Interlocking Machine. — Each lever is connected to a slide 
that moves in a horizontal plane making and breaking the circuit 




Fig. 151. — Section through Hall interlocking machine. 



by means of the controllers attached to the rear of the slide. The 
mechanical locking is of the vertical type operating in practically 
the same manner as that in the Style A machine. The levers 
are equipped with latch pins actuated by the latch handle to serve 



ELECTRIC INTERLOCKING 145 

the purpose of latch locking. ' The levers are also provided v^^ith 
stop dogs to relieve the indication and safety dogs and to leave 
them free to move regardless of the pressure exerted on the lever 
handle. Electric locks are located above the lever slides with 
notches cut in the side to give the desired lever locking according 
to requirements. 

To prevent the movement of a switch lever to full normal or 
reversed position before a proper indication is received, two me- 
chanical locking dogs are arranged in each lever slide. The dogs 
are mechanically forced down into a slot in the bed plate on which 
the lever slide rests, and can be forced out of the slot only by the 
action of the indication and safety magnet armatures. The arma- 
ture of the safety magnet has two vertical lugs projecting up from 
the face of the armature plate which engage with two horizontal 
lugs attached to the lever slide. The function of these lugs is to 
lock the lever in the full normal, reverse and operating positions 
with the safety coil energized. All the current for operating the 
switch must pass through the safety magnet, which has two wind- 
ings, one a low-resistance winding of 0.4 ohm, and the other a 
high-resistance winding of 350 ohms. The high-resistance wind- 
ing is connected in parallel with a fuse, which makes the safety 
magnet effective with or without the fuse in circuit. To make a 
complete movement of the switch lever, it is obvious that the 
safety magnet armature must be energized and then deenergized 
in addition to the energization of the alternating-current indica- 
tion magnet. 

91. Switch Movement. — The switch is thrown by an electric 
motor operating through a train of gears. It is provided with a 
normal and reverse controller, an indication selector, an indica- 
tion transformer, lock rod, throw rod and locking plunger. The 
motor is connected to the gearing by a friction clutch to elimi- 
nate the strain that would arise if the gears should be brought 
to a sudden stop. The controllers are actuated by a cam plate 
rigidly attached to the locking plunger. This makes their action 
positive and becomes dependent upon the actual locking of the 
switch. The plungers are staggered in a horizontal plane so as 
to make it impossible for the normal plunger to enter the re- 
versed notch in the lock rod, or vice cersa. The throw rod, itself, 
is locked in both normal and reverse positions by a peculiar 
arrangement of the gearing, so that the switch cannot be forced 
over by taking off the lock rod. 

10 



146 RAILWAY SIGNALING 

The indication selector is composed of two magnets, one in 
multiple with the reverse operating circuit, and the other in 
multiple with the normal operating circuit. Each of these 
magnets, when energized, operates a set of contacts corresponding 
to the contacts of its respective locking plunger controller so 
that the selector contacts and the locking plunger controlling 
contacts must operate in conjunction. 

92. Switch Operating Circuits. — The circuit for a switch con- 
sists of a normal operating wire shown on the plan as NO, a 
reverse operating wire shown on plan as RO, and a negative 
shown as Neg., Fig. 152. 

The operation is as follows: Operating the lever latch handle, 
closing the lever latch contact LL energizing the lever lock 
L, permits the lever to be moved to the reverse operating position, 
which closes contacts 7-8 and 11-12. Current will now flow 
from 110- volt positive bus over wire 20, 10-amp. fuse, wire 21, 
through low winding SL of safety magnet, wire 22, contacts 8-7, 
wire 23, over RO wire, to RO contact on plunger circuit con- 
troller, over wire 24 through coil RIS on reverse indication 
selector to negative. This will energize the selector aild close 
contacts RO, RI, RP and RD. When these contacts close, 
current will flow through the RO contact on RIS over wire 25, 
through fields RF and motor armature A to negative. Immedi- 
ately the motor starts, the contactors NO, ND, NI and NS on 
normal plunger circuit controller will shift to the right closing 
the NO contact and opening contacts ND, NI and NS. When 
the switch has completed its full movement, the contactors of the 
reverse plunger circuit controller will shift to the left and open 
the RO contact and close the RD, RI and RS contacts. When the 
RD contact is closed, it completes a local dyamic brake circuit 
over wires 36 and 34, through the NF winding, through A to 
negative, to the RD contact on selector, through D winding, to 
RD on plunger circuit controller. This snubs the motor and 
holds the indication selector magnet closed for a predetermined 
interval of time, which is sufficient to allow the indication magnet 
on lever to operate. When the dynamic or snubbing current 
ceases, the selector becomes deenergized and automatically 
opens its contacts. 

93. Signal Operating Circuits. — The operation for a signal is 
as follows: The lever is moved to the full reverse position (no 
reverse indication being required), closing contacts 3-4 and 7-8; 



ELECTRIC INTERLOCKING 



147 



■Sis*^ wt/O-O^ 




4i|i|i|.|i|i|i|iiiP; 











r 



^ 



^ 



:t 



Sij//pj9B'Q jifu£;y 



\* - W^i^/iJi^- ^ ^"--^-v 



El 



lb 



o 

GO 

a 

W) 



148 RAILWAY SIGNALING 

current will then flow from 110- volt positive bus through coil A 
of cross protection relay over wire 40, 5-amp. fuse, wire 41, 
contact 7-8, wire 42, through coil B of cross protection relay, 
wire 43, contact 4-3, signal operating wire to circuit breaker 2 
on signal mechanism, through motor and clutch in multiple to 
negative. 

94. Indication Current. — The alternating current for the signal 
indication circuits and for the primary of the switch indication 
transformer is obtained either from a commercial source of 
supply or is generated at the plant by means of a 3^^-kw. motor- 
generator set operated from the storage battery through contacts 
on each lever. As the motor starting contacts are closed only 
when the lever is in the indication position, no battery c urrent 
is consumed when all levers are in their full positions. The 
primary of the indication circuit is from alternating-current 
supply through the various coils and transformers returning to 
supply on 110-volt negative. The indication magnets are design- 
ed so as to be immune to direct current. The signal lever 
indication magnet is wound to operate direct from the prim- 
ary main. The switch lever indication magnet is wound to 
operate on not less than 250 volts. A one-to-three transformer 
that steps the indication current up to 330 volts is located at 
each switch function. 

95. Switch Indication Circuit. — The normal indication is re- 
ceived from the switch as follows : The primary coil P of indica- 
tion transformer was energized through contact NP of NIS when 
switch movement was started. When plunger operated cir- 
cuit controller contact NI closed, indication current flowed from 
coil S of indication transformer over wire 27, contact NI, wire 
35, contact NI on NIS, over wire 24 to contact RO on plunger 
operated circuit controller, over wire RO, wire 23, contact 9-10 
wire 31, indication magnet I, wire 32, indication bus and indica- 
tion main to coil S of indication transformer. 

96. Signal Indication Circuit. — The signal indication is re- 
ceived when the lever is moved to the normal indication position 
closing contacts 5-6 and 9-10 and contact 4 on signal mechanism. 
(Contact 4 is closed only in zero position of the signal.) The 
current will then flow from the primary main through contact 4 
on signal mechanism over signal indication wire to contact 9-10 
on lever, over wire 45, through indication magnet /, over wire 44, 
wire 43, and through contact 6-5 to negative. 



CHAPTER VIII 

DIRECT-CURRENT TRACK CIRCUITS 

97. Track Circuits. — The direct-current track circuits used in 
power interlocking and in automatic block signaling are operated 
by local batteries. A portion of the track is set apart as a block, 
which has a low-voltage circuit of its own traveling through the 
rails, as indicated in Fig. 153. The blocks are separated by- 
insulated joints, while the rails within the blocks are all bonded 
to insure the continuity of the circuit. At the end of the block 
is an electro-magnet known as a relay, A, that governs the opera- 
tions of the lock or signal, or whatever function is to be controlled. 
When the coils are energized, the armature, B, of the relay picks 
up, making what is termed front contact. When they are de- 
energized, the armature drops away by gravity, making back con- 

Insulafec^ Joints. 

'-^ — — Smm 






Track Baff^rCf 

. M,|.±J 
p 

Fig. 153. — Track circuit diagram. 



tact. These track relays are usually wound to a resistance of 
from 2 to 4 ohms. If it is any less, the armature may not drop 
away when a train comes into the track; if any more, it may not 
hold when the track circuit is temporarily weakened by rain or 
snow, even though there be no train in the block. 

At the opposite end of the block is the track battery, C, for 
which in the plan indicated, the track circuit is always closed. 
When there is no train in the block, the relay is energized, hold- 
ing up the armature which completes the circuit to the signal 
motor and to the mechanism that retains the arm in the proceed 
position. When a train comes into the block, much of the current 
flows across the axles shunting the relay and releasing the arma- 
ture. This breaks the circuit to the motor or holding device, and 
the signal arm goes to the stop position of its own accord. The 
battery and relay should be placed at the extreme ends of the 
block to get the full benefit of broken rail protection. 

149 



150 



RAILWAY SIGNALING 



The voltage of the track circuit varies from H to 2 volts. It is 
made low in order to avoid as much leakage as possible from rail 
to rail across the ballast. It must not be too low, however, or it 
will not operate the relay especially during periods of rain or 
snow, when the leakage is the greatest. If the ballast touches 
the rail, the leakage is considerably increased. As the track 
currents are flowing continuously and as the signal batteries 
are active except when a train is in the block, some kind of battery 
should be chosen that will not become exhausted quickly. 
For this purpose, the primary batteries most commonly used in 
practice are the gravit}^ and the Lelande types. Two or three 
cells of either kind are sufficient for a track circuit. Storage 
batteries are used to some extent on account of the greater output 
per cell. One such cell is generally sufficient for a track circuit. 

The amount of current to operate a 4-ohm track relay alone is 
less than J^ watt. As 50 per cent, of the current in the track 
circuit is lost by leakage and 10 per cent, by overcoming re- 
sistance of the rails, the battery, and the relay, the battery 
output should be about H watt. In most cases, the batteries 
must be protected by inserting some kind of resistancein series 
with the track to reduce the amount of current flowing when a 
train is in the block. 

98. Cut Sections. — Where the blocks become too long for a 
battery to operate the relay successfully, cut sections are em- 



(a) 






w 



nr 



^ 



cw 



rVi 



Fig. 154. — Cut section track circuits. 



ployed. The block is divided into two or more sections with a 
relay and track battery in each. The battery of one section is 
connected through the armature and front contact of the relay 
in the adjacent section so that when the relay of any section is 
deenergized the circuits for all sections in the rear in that block 
are broken. Figure 154a shows a cut section in an ordinary 



DIRECT-CURRENT TRACK CIRCUITS 



151 



track circuit and 1546 a cut section in a polarized track circuit. 
The direction that the current flows through the polarized track 
circuit is controlled by a pole-changer on the home signal. 

99. Fouling Circuits. — FouHng circuits are used for protection 
at turnouts or crossings where there is a possibility of a car stand- 
ing on one track interfering with those moving on another track. 
For example, a car standing too near the frog in a turnout may 
endanger the movements of trains on the main Hne. The fouling 




Fig. 155. — Fouling circuits at a turnout. 

circuits generally extend to the clearance point of the siding, 
which is frequently marked by a derail. 

Figure 155 shows a wiring plan for an insulated switch protected 
to the clearance point of the siding. A pair of wheels standing 
at any point on the turnout up to the clearance post will give to 
the block signal a stop indication just as if a train were oc- 
cupying the main track. 

Figure 156a shows a wiring diagram for a crossover between 
two main tracks controlled by block signals. Figure 1566 repre- 




FiG. 156. — Fouling protection at crossovers. 

sents another form of track circuit so connected through the 
switch controller that the opening of the switch on either track 
will operate to throw the approaching signals to the stop 
position on both tracks. 

100. Insulated Rail Joints. — In order to separate the rails elec- 
trically at the ends of a block, some kind of vulcanized fiber is 
ordinarily used, placed between the ends of the rails, between the 
spHce bars and the rails, and around the bolts that hold the splice 
bars in place. Occasionally on low-speed tracks, wooden-block 



152 



RAILWAY SIGNALING 



splice bars are used on each side of the rail instead of metal bars, 
in which case the only fiber necessary is that between the ends of 
the rails. Figure 157 shows some of the different types of 
joints commonly found in practice. 

101. Rail Bonds for Track Circuits. — As the construction of the 
rail joint itself is an uncertain factor in the continuity of the 
track circuit; and as a scale of rust, which is a poor conductor 
of electricity, is likely to form between the splice bar and the 
rail, the intermediate rail joints in the block are all bonded. 
Where there is no return propulsion current to carry, two No. 8 
B.W.G. galvanized iron wires are generally used. One wire is 




Fig. 157, Part 1. — Insulated rail joints. 

sufficient to carry the track current, but an additional one is used 
to provide for breakage or other failure. Holes are drilled 
through the web of the rail near the end of the splice bar, and the 
iron wires are held in place in these holes by copper-plated steel 
channel pins driven in around the wire. The bonds are generally 
placed outside of the angle bars to permit an easy inspection for 
broken wires. Where there is a propulsion current to consider, 
however, heavy copper bonds are required at each joint, adding 
a considerable item of expense. 

102. Neutral Relay. — The two coils of the relay shown in 
section in Fig. 159, are protected from mechanical injury by 
hard rubber shells, M, or by insulating varnish. The wires that 
energize the coils are connected to the two binding posts, P. 
The armature, A, is hinged at the back of the poles and very 



DIRECT-CURRENT TRACK CIRCUITS 



153 




Continuous. 




Weber. 




Keystone. 
Fig. 157, Part 2. — Insulated rail joints. 



154 



RAILWAY SIGNALING 




Rail bond for track circuit. P. & M. bond protector. 




'^ Tap er with aifuj^per fti] 



<?.2<?4M 



Total Tap&r^ "per ft. 

R. S. A. channel pin, plan 1086. 
FiQ. 158. — Rail bonds for track circuits. 





INVERTED PLAN VIEW 
BOTTOM PLATE REMOVED 




FRONT VIEW 
GLASS SECTIONED 




SECTIONAL SIDE VIEW 

Fig. 159. — Neutral relay. 



DIRECT-CURRENT TRACK CIRCUITS 



155 



little movement is necessary to make and break contact. Two 
small non-magnetic stops attached to the lower end of the pole 
pieces provide a slight air gap between the pole pieces and the 
armature, thereby eliminating the possibility of the armature's 
sticking on account of residual magnetism in the cores. The 
contact fingers, K, are fastened to the armature by bakelite 
studs so as to insulate them electrically. The tips of the fingers 
where they touch the front and back contacts are made of silver 
or platinum. The circuit for front contact is made through the 




Fig. 160. — Neutral relay. {Union Switch & Signal Co.) 

binding post F and back contact through the post B. One 
terminal of the control circuit is fastened to the binding post G 
and the other to i^ or 5 according to whether front or back 
contact is required. The armature and contact fingers are 
enclosed in a transparent dustproof case to protect them from 
dust and moisture and from mechanical injury. While the wind- 
ings for practically all track relays vary from 2 to 4 ohms, the 
resistance for line relays runs much higher, even up to 1,000 ohms. 

A comparison of the 2- and 4-ohm relays printed in the Pro- 
ceedings of the Railway Signal Association presents the following 
points for consideration:^ 

1 Page 5, 1918. 



156 RAILWAY SIGNALING 

1. Because of its lower operating voltage, the 2-ohm relay will operate 
with a lower ballast resistance. 

2. The 2-ohm relay is less susceptable to leakage current from adjacent 
battery entering track circuit through insulated joints. 

3. The energy consumption for the 2-ohm relay on equal track circuits is 
approximately 50 per cent, less when the track is occupied. When the 
track is not occupied the energy consumption will be less when the ballast 
resistance is less than 5 ohms per 1,000 ft. 

4. The length of track circuit may be increased with the use of the 2-ohm 
relay if no foreign current is present and the resistance between the battery 
and track is not less than the recommended limiting resistance. 

5. On track circuits of equal length the 2-ohm relay gives equally as 
good protection against broken rails where no foreign current is present. 

6. On track circuits of equal length, the 2-ohm relay will release with a 
higher shunting resistance across the rails when foreign current entering 
the track circuit is less than 350 amp. 

7. Considering track circuits of equal length and with other conditions 
equal, no definite recommendations can be made in favor of either the 2-ohm 
or the 4-ohm relay where foreign current is present, on account of there 
being conditions where each has its advantages over the other. 

8. With a foreign current present, the 2-ohm relay on a track circuit of its 
maximum operable length will receive more combined foreign and track 
battery current than will be received by a 4-ohm relay on a track circuit of 
its maximum operable length. 

9. When a battery lead or a rail is broken and the track circuit between 
the break and the relay is shunted, the 2-ohm relay will be more susceptible 
to foreign current than the 4-ohm relay. With the track circuit not shunted, 
the 2-ohm relay will be more readily picked up by foreign current only 
when that current enters the track circuit through a resistance less than 
5 ohms. 

In view of the above statements, your Committee recommends the use of 
the 2-ohm relay with caustic soda battery, provided the recommended 
limiting resistance is used in series with the battery. The recommended 
limiting resistance should also be used in series with the battery wherever 
the 4-ohm relay is used with caustic soda battery. 

103. Polarized Relays. — In addition to the two coils found in 
the neutral relay, there is a steel bar, P, that is permanently 
magnetized in the polarized relay, Fig. 161. The polarized 
armature, PA, rotates in a horizontal plane about a vertical 
axis through X. The armature is supported between the lower 
end of P and the bracket S. The top of the permanent magnet 
is generally the north pole and the bottom the south pole. The 
entire polarized armature then becomes a south pole by induction. 
The polarized armature can operate only when the neutral relay 
is energized, at which time one of the pole pieces of the coils 
becomes a north pole and one a south pole. The north pole 



DIRECT-CURRENT TRACK CIRCUITS 



157 



will attract the polarized armature while the south pole will 
repel it, causing a slight rotation. The fingers, K, connected to 
the armature by insulators, make contact connections with the 
binding posts B. 





INVERTED PLAN VIEW 
BOTTOM PLATE REMOVED 




FRONT VIEW 
GLASS SECTIONED 



Fig. 161. 



SECTIONAL SIDE VIEW 

-Polarized relay. 



104. Track and Signal Batteries. — The electrolyte of the 
gravity cell is made up of two liquids that separate themselves 
by gravity. A saturated solution of copper sulphate is used 
in the lower half of the jar and a dilute solution of zinc sulphate 
in the upper half. The copper element rests on the bottom of 
the jar in the copper sulphate solution and the zinc element is 
supported at the top in the zinc sulphate solution. The gravity 
cell finds its best service where the current demand is practically 
continuous as it is in the case of the track circuit. Where the 
current is broken for some time a chemical change takes place 
that practically destroys the efficiency of the cell. As the cell 



158 



RAILWAY SIGNALING 



must be renewed about once a month, it involves considerable 
expense for maintenance. The internal resistance of the cell is 
very high. 



PORCELAIN COVER 




-^l 



PORCELAIN JAR 



^#--##- 



^A 



Caustic Soda Signal Cell 

tAOO Ampere hours) 

R. S. A. 



NOTES. 

COMPLETE CELL. A complete cell consists of a 
jar, cover and renewal with one hexagon nut, two 
wing nuts and two washers as shown. 

RENEWAL. A renewal consists of a sealed can of 
caustic soda, sealed bottle of mineral oil and the as- 
sembled elements with connecting wire and rigidly 
connected suspension bolt. Nuts and v/ashers shall 
be furnished with renewals only when specified. 

The elements shall be so assembled that when at- 
tached to the cover and the nut on the upper side 
tightened to place, the elements will be at the proper 
height in the solution. 

Connection to zinc shall be No. 12 B & S gauge solid 
soft drawn copper wire covered with an insulation 
suitable to withstand the action of the oil and elec- 
trolyte. Insulation on end of wire shall be trimmed 
either tapered or square and in this operation the wire 
must not be scored. 

Suspension bolt shall be iron, copper plated. 

JAR AND COVER. Jar and cover shall conform to 
the dimensions shown, with reasonable allowance for 
slight irregularities in manufacture. Top of jar 
shall be square with vertical axis and cover shall be 
perfectly flat. Manufacturer's name or trade mark 
may be shown on cover. Porcelain jars shall be glazed 
inside and out and covers on top and edge. 

A solution line consisting of a slight ridge or depres- 
sion extending around the inside of porcelain jars 
and the outside of glass jars shall be placed as shown. 

For heat resisting jars, glass shall be three-sixteenths 
inch 1 3/16".' thick and inside dimensions shall be as 
shown with reasonable allowance for slight irregulari- 
ties in manufacture. 



1053 



Fig. 162. — R. S. A. standard caustic soda signal cell. 



The Lelande type covers a number of patented cells, among 
which are the Edison, Columbia, Waterbury, and Gordon, 
varying only in the method of construction. The electrolyte 



DIRECT-CURRENT TRACK CIRCUITS 



159 



■^4. 



is a strong solution of caustic soda, while the elements used are 
zinc and copper oxide. The cells do not 
deteriorate when not in service and may be 
used on either open or closed circuits. As the 
total output of the cell is practically constant, 
a heavy current may be drawn for a short time 
or a low current for a long time. As used in 
ordinary signal practice, the cell must be 
renewed about every eight or nine months. 
The internal resistance of the cell is so low 
as to require some kind of resistance in series 
with the battery to prevent it from becom- 
ing exhausted too quickly when used on track Fig. 163.— Edison 

circuits. primary cell. 





Fig. 164. — Waterbury signal cell. 



The storage cell is formed of two lead plates with an electro- 
lyte of dilute sulphuric acid. The plates of themselves will not 



160 



RAILWAY SIGNALING 




Fig. 165.— 
Columbia signal 
cell. 



form a current as the primary batteries do, but must be charged 
by the current from a generator or from a mercury rectifier. 
Once so charged, they will give out current, but they must be 
recharged rather frequently. They possess the advantage, how- 
ever, of having a higher voltage, each cell having an electro- 
motive force of 2 volts. 

r 105. Battery WeUs and Battery Chutes.— 
^/^ ^ The batteries used to operate the signals are 
generally housed in battery wells, located near 
the base of signals. Most of these wells are now 
made of concrete, as illustrated by Fig. 166. 
They are built in a material yard, and shipped to 
the place where they are to be used. Some are 
set into the ground to within a foot of the top, 
while others are set with their tops flush with the 
surface of the ground. This not only provides a 
safe place where the batteries will not be dis- 
turbed, but also protects them against freezing 
temperatures. The well is usually 4 or 5 ft. in 
diameter and from 4 to 8 ft. in depth over all. 
Tiers of wooden shelves are provided around the wall of the 
well to support the battery cells. 

The two or three cells required for the track battery when 
housed alone are generally placed in a battery chute, the greater 
portion of which extends below the ground. The chutes are 
usually made of cast iron, just large enough in diameter to con- 
tain the cells when they are supported one above another. The 
length of the chute varies from 5 to 7 ft.; but even longer ones 
are used where the temperature gets low enough to require the 
cells to be placed at greater depths to prevent freezing or 
to maintain the proper efficiency. About a foot of the chute 
remains above the ground; and some proper construction 
is utiUzed to so connect it with the trunking that the wires 
will not be exposed to the weather. In order that they 
may be easily removed for repairs or renewals, the battery 
cells are supported in wooden elevators raised and lowered by 
a rope. 

106. Cable and Relay Posts. — Cable posts are used to house 
and support wires where connections are made between lines 
and relays. At points where it becomes necessary to install a 
relay in its own housing, the relay box is generally attached to 



DIRECT-CURRENT TRACK CIRCUITS 



161 



the cable post, as shown in Fig. 167. Figure 168 represents a 
battery chute with a relay box attached. 

107. Trunking. — The trunking used to carry the wires from the 
track connections to the battery wells and battery chutes, to 
the track relays and the signal towers, is generally made of wood, 
frequently treated with some chemical agent to protect it against 




Fig. 166. — Massey 80-cell battery well. 

decay. As shown in Fig. 169, it may be either grooved or built- 
up depending upon the size of the opening required. The trunk- 
ing is buried flush with the surface of the ballast when used within 
the roadbed, and is supported on substantial taskes when carried 
along the ground. Conduits of fiber and other materials are 

sometimes used, but they are laid underground and are generally 
11 



162 



RAILWAY SIGNALING 



encased in concrete. Reinforced concrete makes a practical 
trunking where it becomes desirable to install a more permanent 
type. 

108. Insulated Head, Front, and Tie Rods. — In order to main- 
tain the track circuit intact through the turnout, all connections 
between the two rails, such as head, front, and tie rods, and 
the head plate where it is used, must be insulated. The common 
method of doing this is to make these rods and plates in two 




Fig. 167. 



-Cable and relay post, 
indicators. 



Switch 



Fig. 168. — Battery chute 
and relay box. 



pieces and bolt them together with a fiber insulator between, as 
shown in Fig. 171. 

109. Lightning Arresters. — -In order to protect the relays and 
other equipment in track and signal circuits against damage by 
lightning, two different appliances have been devised to insert 
in the circuit — the spark gap arrester and the choke coil. One 
type of spark gap arrester frequently used is made of five brass 
plates arranged as shown in Fig. 172, with a short air gap between 



DIRECT-CURRENT TRACK CIRCUITS 



163 



rr^r -^ 



v 

^ 



X 



^^--1 i 



-5i--> 



v^^^^^ 



Mc^ 



Fig. 169. — Trunking and capping. 




Fig. 170. — Reinforced concrete trunking on Xew York Central R. R. at Utica, 

N. Y. 




Fig. 171. — Insulated switch rod. 



164 



RAILWAY SIGNALING 




Fig. 172. — Hall lightning arrester. 




Fig. 173. — Lightning arresters in relay box. 



DIRECT-CURRENT TRACK CIRCUITS 



165 



them. The center plate is grounded; the other four are connected 
to the track and other circuits. As the hghtning has a high 
voltage, it will tend to jump the gap rather than follow the wires, 
and the notches on the edges of the plates will aid the discharge, 




Fig. 174. — Hall choke coil lightning arrester. 



The choke coil is generally made by winding a bare copper 
wire into a coil around a procelain core. The direct current of 
the track or signal circuit will meet with practically no resistance 
in the coil ; but the lightning, being a high-frequency alternating 
current, will meet with an impedance due to the self induction of 
the coil. 



CHAPTER IX 

ELECTRIC LOCKING 

110. Wiring Diagrams for Electric Locks. — Figure 175 is the 
Union method of wiring for operating a power distant signal in a 
mechanical interlocking plant. When the home signal, 2, is 
cleared, its circuit breaker, C, is closed so that when lever 1 is 
reversed, the circuit is complete to relay D picking up its arma- 
ture and closing the local battery circuit to clear distant signal 1. 



Bi 



Ur 



J 



IS 



nf. 



Fig. 175. — Wiring for power distant signal. 

The signal will remain cleared until lever 1 is returned to its 
normal position. 

Figure 176 is an indication wiring so arranged as to make cer- 
tain that the distant signal is returned to its full normal position 
before the lever latch can be released. When lever 1 is reversed 
after signal 2 is cleared, the distant blade will go to clear. Levers 




Fig. 176. — Wiring for electric lock. 

1 and 2 may be returned to their normal positions, but the latch 
on lever 2 will not be released until the distant blade goes to its 
full normal position closing circuit breaker F, thereby energizing 
lock A on lever 2 and unlocking its segment 2. The latch will 
then be dropped into its full normal position. If F is not closed 
however, A will not be energized and the latch will remain locked. 

166 



ELECTRIC LOCKING 



167 



Figure 177 shows a form of an electric lock to control the lever 
latch on a Saxby and Farmer machine. In Fig. 178 an arm 




Fig. 177.— Electric lock. 




c- 




Fig. 178.— Electric lock. 



fastened to the locking shaft D operated by the latch, is connected 
by means of link F to a segment A that rotates about its center C 



168 



RAILWAY SIGNALING 



The edge of this disc engages a bar, B, controlled by the electro- 
magnet. When this lock magnet becomes energized, the bar, B, 
is raised clear of the notch allowing the locking shaft to be turned 
and the latch to be seated in its normal position. 

Figure 179 shows a lock applied to a Saxby and Farmer 
machine. It is connected by a rod directly to the rocker-link 
manipulated by the lever latch. When the magnet becomes 
energized, its armature lifts the dog from the segment notch 




^^=:-0^W^-^:^^^ 




Fig. 179. — Electric lock applied to a mechanical interlocking machine. 

allowing the rocker-link to be moved by the lever latch. Figure 
180 shows enlarged views of the lock. 

Figure 181 is an arrangement by which the distant signal is 
controlled through the home signal and a section of bonded track, 
or a track circuit section. When the home signal, 2, is cleared, 
the circuit breaker A completes the circuit through the track 
battery C, energizing the track relay E, thereby completing the 
local battery circuit through signal F causing it to go to the clear 
position. As soon as a train enters the controlling track section, 



ELECTRIC LOCKING 



169 



relay E is deenergized causing the signal F to go to the caution 
position. When signal 2 returns to the normal position, circuit 
breaker A opens the circuit that controls the relay E, and signal 
F will continue in the normal position. Signal F, brought to the 
clear position by power controlled by the towerman in the inter- 




SIDE VIEW COVER SECTIONED 



END VIEW COVER SECTIONED 



Fig. 180.— Details of electric lock. 



locking plant, but returned to its normal position by the presence 
of a train in its track section, is called a semi-automatic signal. 
Figure 182 is an elaboration of the wiring arrangement shown 
in Fig. 181 whereby the lever to home signal 2 may be locked in 
the half reversed position. Z) is a circuit breaker on the drum of 



1-4-, 



ISI 



ii 



-tr-*- 






Fig. 181.^ — Distant signal controlled by track circuit. 

the electric lock that is closed when lever 2 is returned to its 
normal position; but A will not become energized until. the distant 
signal has gone to the full caution position, closing the circuit 
breaker J. As soon as A becomes energized, the latch is un- 
locked and may be placed in its normal position. 



170 



RAILWAY SIGNALING 



Figure 183 is an arrangement whereby the distant signal and 
the tower indicator B are controlled by a short track section 
known as a '' setting section. '' The section may be made as long 
as desired, but a few rail lengths will answer the purpose. When 



aJ? 






L 






LtfJfc 



E r 

Fig. 182. — Electric lock applied to Fig. 181. 

the home signal E is cleared, circuit breaker D is closed. If after 
lever A is reversed, the armature is lifted to close the front contact 
of relay B, B will become energized by battery C provided there 
is no train on the track section between the two sets of insulated 



-THimt: 









i- 

Fig. 183. — Distant signal controlled by setting section. 

rail joints, and the armature of B will stick. As soon as F be- 
comes energized by battery C, the distant signal goes to clear. 
Should a train come into the block, the signal would return 
to caution and would remain in that position after the 



T 



-^l|l|H^ 



Li 




Fig. 184. — Setting section and electric lock. 

train goes through. As soon as J becomes deenergized, B 
becomes deenergized and its indicator goes to the stop posi- 
tion, opening the circuit until restored by hand. 



ELECTRIC LOCKING 171 

Figure 184 is an elaboration of the wiring arrangement shown 
in Fig. 183 and provides for a separate lever to operate the distant 
signal in connection with the track section and an electric lock D 
to insure that the distant signal blade returns to its full normal 
position. Levers 1 and 2 may be returned to normal, but 2 will 
remain locked in the half reversed position until circuit breaker 
J is closed. 

111. Section Locking. — As defined by the Railway Signal 
Association, section locking is: ''Electric locking effective while 
a train occupies a given section of a route and adapted to prevent 
manipulation of levers that would endanger the train while it is 
within that section." 

The introduction of heavy track rails has rendered more or less 
uncertain the effectiveness of the detector bar in preventing the 




^■'^-^ 



"^f f/ecfr/'c Lock on F.PL G 
Fig. 185. — Section locking. 

signalman from throwing a derail or switch under a train. With 
the wide rail, there is a possibility that the detector bar would 
miss the tread of the wheel entirely if an attempt should be made 
to throw the switch under a train, and thus it would fail to per- 
form the only function it had to serve. Furthermore, the clips 
sometimes fail either from continual wear or from the force of 
the drive by power equipment. 

As a measure of greater safety, section, or detector locking, is 
used sometimes instead of the detector bar and sometimes in 
addition to it. It becomes effective by having electric locks 
attached to the facing point locks or to the switch levers and 
controlled by the track relays. The track section used for this 
purpose may vary from 100 to 300 ft. in length. Figure 185 
shows circuits for section locking. 

As the lock is controlled by the track relay, the lever to which 
the lock is attached is locked positively in both the normal and 
reverse positions as long as the track section is occupied by a 
train. On certain occasions while a train is standing in a portion 



172 



RAILWAY SIGNALING 




Fig. 186. — Electrical screw hand release. (General Railway Signal Co.) 



ELECTRIC LOCKING 



173 



of this section, it might become desirable to energize the electric 
lock in order to change the route. To accomplish this, a screw 
release is inserted to energize the lock magnet independently of 
the track section. A floor push is installed in the locking circuit 
as a matter of economy in current consumption. 

112. Screw Release. — A screw release is a device for mechani- 
cally releasing the electric lock on a lever in a mechanical 
interlocking plant in order to restore the levers to their normal 
position with or without the section having been occupied by a 
train, depending upon the particular case in hand. It intention- 
all}^ involves an element of time either to prevent hasty action on 




Fig. 187. — Clock-work time release. 



part of the towerman in some cases or to penalize him for negli- 
gence in other cases. 

An electrical screw hand release is shown in Fig. 186. In 
its normal position, the contact block is as far to the upper end of 
the screw as it is possible to go. To manipulate the electric 
lock, the contact must move the full length of the screw, requiring 
from one to two minutes of time for the operation. It is known 
also as a hand release, time release, and slow release. 

113. Clock-work Time Release. — ^The clock-work time re- 
lease, shown in Fig. 187, serves the same purpose as the hand 
release, but requires very little of the signalman's time for actual 
manipulation. To apply the release, he turns the knob as far to 



174 RAILWAY SIGNALING 

the right as it will go. This winds up a mechanism of clock-work, 
which when released slowly unwinds, returning the pointer to its 
stop position. The time interval is usually from one to two min- 
utes, but may be as much as four. When there are many move- 
ments of trains, however, the interval must be comparatively 
short. 

114. Approach Locking. — As defined by the Railway Signal 
Association, it is: ''Electric locking effective while a train is 
approaching a signal that has been set for it to proceed 
and adapted to prevent manipulation of levers or devices that 
would endanger that train. " 

Approach locking is an arrangement whereby, after a train has 
passed a certain point or entered a certain route approaching an 
interlocking plant, the route cannot be changed after the signals 
have been accepted. It is used essentially at high-speed points 
for a greater protection than the ordinary crossing signals give. 
In this connection, there is usually a preliminary track section 
outside of the section governing the distant signal. When the 
train enters this preliminary section and the home signal has 
been cleared the route cannot be changed except by the hand 
release. As soon as the train has passed the home signal, the 
locking is released. Some type of indicator controlled by the 
preliminary section or by the entire route is generally used in 
connection with approach locking. 

Figure 188 is the Union arrangement for approach locking used 
in connection with the lever controlled power distant signal. 
After signal 2 is cleared and its circuit breaker is closed, lever 1 
may be reversed placing distant signal 1 in the clear position. 
When a train enters the preliminary section Y-Z, it deenergizes 
the lock magnet B. Levers 1 and 2 can be returned to the fuH 
normal position, but the latch on lever 2 will be locked half re- 
versed until the train passes X. When both track sections are 
cleared, the lock B becomes energized, unlocks the latch and allows 
it to be seated in its full normal position. 

It sometimes becomes desirable to change the line-up of the sig- 
nals after a train has stopped between X and Z in Fig. 188. To do 
this, a screw release or time lock is provided. Figure 189 shows a 
hand release, also an approach indicator added to the arrange- 
ment in Fig. 188. When the train occupies the track between X 
and Z in Fig. 189, the tower indicator A becomes deenergized 
thereby locking signal lever 2 in the half reversed position. To 



ELECTRIC LOCKING 



175 



change the Une-up in any way, the latch on lever 2 must be re- 
turned to the full normal position. This is done by means of the 
screw release. The lock magnet is a relay, which becomes 
energized when the lower contact of the screw release is closed 
through a circuit not controlled by the indicator. As soon as the 
lower contact is made, the latch on lever 2 may be returned to the 



3-/ 



i|i|iii^ 



u' 



rain Eg 



m^ 



m-Mv. 



Fig. 188. — Approach locking. 

full normal position, allowing for a change in line-up of the tracks. 
When the lower contact is made, the upper contact is broken. 
The upper contact must be closed again by the screw release 
before the distant signal can be cleared. 

Figure 190 is a form of approach locking with semi-automatic 
control of the power distant signal through the contact of the 
tower indicator with relief for changing the line-up by means of 



I 



si 



BriiE^^^ 



Fig. 189. — Approach locking. 

the screw release. Distant signal D is cleared as soon as home 
signal 2 is cleared by a current from battery A through upper con- 
tact of screw release R, contact on hard rubber drum of lock iV, 
front contact of second armature J, circuit breaker M, line relay 
L, and return to A, energizing hne relay L. When the relay L 
becomes energized, the local circuit through battery 5 is complete 



176 



RAILWAY SIGNALING 



to operate signal D to clear. The distant signal goes to caution 
as soon as a train enters the section G-H. When there is no train 
in this section, the track indicator J will indicate clear only pro- 
vided the towerman has placed signal lever 2 in its normal posi- 
tion after the passage of the last train. 

The signal lever 2 may be returned to its normal position at any 
time, but its latch cannot be released until the block G-K is un- 
occupied and the distant signal is placed at caution. This prevents 
the towerman from quickly taking the signals away from a train 
after they have been accepted and throwing a derail in front of the 
train. If the block G-K is occupied by a train and the lever 
latch 2 is in a half reversed position, it cannot be restored to a full 
normal position except the train move out of the block or the 
towerman use his screw release. 




Fig. 190. — Approach locking. 



115. Route Locking.^ — The Railway Signal Association's defi- 
nition of route locking is: "Electric locking taking effect when 
a train passes a signal and adapted to prevent manipulation of 
levers that would endanger the train while it is within the limits 
of the route entered. " It is an extension of section locking such 
that all switches and derails within the limits of the track to be 
protected by route locking are locked automatically by a train 
entering the route and remain so locked until the train leaves the 
route. It should take effect when the train passes the first signal 
on the route. Some means should be provided that the route 
line-up may be changed should a train stop in the route, but it 
must be a slow process requiring a time element for protection. 
A hand or time release is used in such instances. Figure 191 
shows an example of both approach and route locking. 



ELECTRIC LOCKING 



177 



In this figure signal 3 in a proceed position presupposes that 
F.P.L.5 and switches 4 and 6 are in proper position for main hne 
movement from A towards D. Before either 4 and 6 can be 
changed for a different Hne-up, it is necessary to place lever 3 and 
then 5 in the full normal position. As soon as the train enters 
section A the approach indicator AB becomes deenergized, 
deenergizing, in turn, the lock magnet on lever 3. The towerman 
may return lever 3 as far as it will go towards its normal position, 
but he cannot release the latch until AB becomes energized again, 
which will be when the train passes out of B into C. He cannot 
move 4 and 6 until the latch on 3 is released. Furthermore, he can 
not change either switch while a train is in C because of section 
locking. 




Fig. 191. — Approach and route locking. R. S. A. plan 1149. 



116. Sectional Route Locking. — Sectional route locking is 
defined by the Railway Signal Association as: ''Route locking so 
arranged that a train in clearing each section of the route releases 
the locking affecting that section." 

By this system as soon as the train enters the route, all the 
signals, switches, and derails on that route are locked as before; 
but as soon as each section is cleared by the train, the locks in that 
section are released. This finds its best service in busy terminals, 
where extraordinary protection is required, but where the train 
movements are so frequent as to prohibit the long time intervals. 

117. Stick Locking. — The Railway Signal Association defines 
stick locking as: ''Electric locking taking effect upon the setting 
of the signal for a train to proceed, released by a passing train, 
and adapted to prevent manipulation of levers that would 
endanger an approaching train. " 

12 



178 



RAILWAY SIGNALING 



Stick locking does not depend upon the presence of a train, but 
becomes effective upon the reversal of the home signal lever. It 
remains effective until the train passes the home signal into the 
releasing section; and unless the towerman returns the lever to its 
normal position while the train occupies this releasing section, he 
must use his hand or time release to do so. Figure 192 is an 
example of stick locking, which involves the use of a stick relay. 
This is Railway Signal Association plan 1151 with some lettering 
added to assist in the explanation, and the floor push substituted 
for the latch. 

When the home signal lever 3 of this plan is reversed, the 
circuit is broken by circuit breaker F on signal 3 and the stick 
relay K becomes deenergized. This, in turn, breaks the circuit 
from battery E through the second contact of R, wire T, lock 



"V ij^nP" 



p^^tt:^ 



i£ 



Lock on Lever 3\j> ^ 



Fig. 192. — Stick locking. 



magent 0, floor push, contact of time release, contact on relay K 
to battery ^, deenergizing O. When the train enters the block C, 
track relay R becomes deenergized, and if the signal lever is 
restored to normal before the train leaves the section C, relay K 
will be reenergized through the back contact of R. While the 
lever may be restored to the normal position, its latch cannot be 
released until unlocked by 0. R will become energized as soon 
as the train leaves the section C, and immediately the lock 
becomes energized unlocking the latch and allowing it to fall to its 
normal position. The fact to be observed is, however, that the 
latch cannot be released in this manner unless the lever is placed 
in its normal position while a train is in section C. If the signal- 
man neglects to restore the lever to normal while the section is 
occupied by the train, or if he lines up a route and the train for 
some reason or another does not come into the interlocked section, 
or if he lines up a route and decides to change it to another, he 
must use his hand release to do so. In the first instance, this 



ii 



ELECTRIC LOCKING 



179 



penalizes him for his negligence, and in the last instance it pre- 
vents him from throwing a derail in front of a train after it has 
passed the distant signal giving a clear indication. The time 
element involved should be enough to allow the train to be over 
the crossing and gone or to allow the train to come to a stop 
before it reaches the home signal. 

118. Stick Relay. — A stick relay, represented by Fig. 193, is so 
connected that its armature and front contact are used to com- 
plete the circuit that energizes its own coils. A circuit from 
battery B through wires 1, 2, and 5, must be provided originally 
to energize the relay R. When A is picked up another route 
formed is from battery B through wires 3, 4, and 5; and the cur- 
rent will continue to flow through it even though the original cir- 
cuit be broken at C. If the ''stick " circuit is broken at any point. 



_ B 



m^ 



r^ 



Fig. 193.— Stick relay. 



as by the deenergizing of a track relay where its armature forms 
a part of the stick circuit, the relay R becomes deenergized 
and the armature A will not pick up until the original circuit 
is closed. 

119. Check Locking. — Where two interlocking plants are 
located a comparatively short distance apart on a single-track road, 
it becomes necessary at times to so interlock levers in the two 
towers that conflicting movements of trains will be impossible. 
Such an arrangement is called check locking. Figure 194 shows 
such a check locking circuit. where there is no preference as to the 
direction of traffic. There is a check lock lever in each plant A 
and Z so interlocked with the signal levers that the signal levers 
cannot be placed in the proceed position until their respective 
check lock levers have been moved to the full reverse position. 
By referring to Fig. 194 it will be seen that as only one of the 
check lock levers can be placed in the full reverse position at a 
time, it will be impossible to clear but one signal at a time; that is, 



180 



RAILWAY SIGNALING 



20 cannot be cleared while 1 is cleared. As the signal lever at 
both A and Z when reversed, locks its check lever reversed, the 
check lock lever must be fully reversed before the signal lever can 
be reversed. The two check lock levers are each equipped with a 
half reverse lever lock that can be energized only when the two 
sets of devices are in a certain position. The signalman in tower 
A may reverse his check lever lock to the reverse indication point, 
but he cannot move it any farther until the lever lock becomes 
energized in the following manner. 

Current from the battery at Z flows through the normal circuit 
controller of the check lock lever at Z, then through the front 
contact of the track relay X, and on through the reverse circuit 



LEVER LOCK 1 f—LATCH CO^mCT 



.R LOCK 1 I — L AfCM CUNIA 



REVERSE W POINT 



^ 






t^ 



^ 



SIGNAL LEVER TAPPET 



BELAY X 



\ 



Fig. 194. — Check locking circuit. For use where there is no preference as to 
direction of traffic. (General Railway Signal Co.) 



controller of the check lock lever at A, and to the lever lock 
itself. After the lock becomes energized, the lever may be 
placed in the full reverse position, whence the signal lever 1 may 
be cleared. The check lock lever at Z may be reversed to the 
indication point, but it cannot be reversed beyond that point 
because its lock magnet cannot be energized. Thus signal 20 
must remain at the stop indication until 1 is restored to normal. 
As only one of the signals can be cleared at a time, traffic can be 
given a proceed indication in only one direction at a time. On 
account of the fact that the relay X, operated by the track cir- 
cuit between the two towers, controls the check lever lock cir- 
cuits, it is impossible to reverse the signal indications while a 
train occupies the track between A and Z. 

120. Union Electro-mechanical Slot. — The up-and-down rod, 
which is pushed upward to clear the signal, is made in two parts, 
A, and B, Fig. 195, and is so connected by the electro-mechanical 



ELECTRIC LOCKING 



IcSl 




Fig. 195. — Union electro-mechanical slot. 



182 



RAILWAY SIGNALING 



slot mechanism that when the magnet ilf is energized the signal 
can be cleared, but when it is deenergized the signal cannot be 
cleared even though the portion of the rod A be raised. The 
two bars, L and T, form a toggle hinged at 0, G, and S. Any 




Fig. 196. — Hall electro-mechanical slot. 

upward thrust on A tends to throw the roller G to the left on 
account of the weight of the signal arm and the rod B, When 
the magnet M is energized this side thrust is resisted by another 
toggle hinged at N, P, and Q and held in position by the armature 
R. Thus, the up-and-down rod is made rigid and the signal 



ELECTRIC LOCKING 



183 



can be cleared. As the three points, N, P, and Q, are not in 
line, the two pieces N-P and P-Q will buckle as soon as the magnet 
becomes deenergized if there is any pressure applied, during 
which time the signal arm cannot be cleared. 

At the top of the encasing iron box is a dashpot installed 
to relieve the force of the blow as the blade comes to the stop 
position. The magnet, M, is controlled by track circuits and is 
energized continuously except when the track section is occupied 
by a train. The spring F tends to hold the lever L in position 




Fig. 197. — Tower indicator. 



against T when the rod A is normal so that the magnet can get 
control of its armature R. The lever must be placed in its 
normal position again before the signal can be cleared. 

121. Hall Electro -mechanical Slot. — In the Hall type of slot, 
shown in Fig. 196, A represents the lower portion of the up-and- 
down rod, or that portion that connects directly to the signal 
lever, and B the portion fastened to the signal arm. A is large 
enough to allow B to slide inside it. A pin C passes through the 
lower end of B and extends far enough out on each side to engage 
the outside rod at the top of the slot S, Both rods are notched 
at N to receive the point of the latch L. M is an electro-magnet 
with an armature, R, connected to the arm E. When the 
magnet is energized the arm E presses against the roller D on the 



184 



RAILWAY SIGNALING 



lower end of the latch and causes the point G to engage both A 
and B so that when A is raised to clear the signal, B moves also 
and the signal goes to clear. Should a train enter the block 
when the signal is clear, the magnet, M, would immediately 
become deenergized allowing E to move away from D, whereas 
the weight of the signal arm and rod B would force the point G 
out of the notch in rod B and the signal would go to the stop 
position. The spring F tends to keep the arm E and the armature 
R in contact with the magnet M, The signal cannot be cleared 
again until the lever is placed in the normal position and the 
magnet is energized. K is an ordinary dashpot used to relieve 







Fig. 198. — Tower indicators. {Hall Switch and Signal Co.) 

the shock of the signal when the blade goes to stop. The 
magnet M is controlled by track circuits and is energized con- 
tinuously except when the track section is occupied by a train. 
The semi-automatic feature of these signals permits them to 
go to the stop position automatically even though the operator 
does not restore his lever to the normal position, an arrangement 
that operates on the side of safety to prevent a following train 
from entering the block until authorized to do so. The magnet 
is controlled by a short track section; and so long as the track 
circuit is not occupied by a train the signal can be cleared, but 
as soon as a train enters the section the slot magnet becomes 
deenergized allowing the signal to go to the stop position. 



ELECTRIC LOCKING 185 

122. Tower Indicators. — Tower indicators are used to notify 
towermen of the approach of trains and to aid them in following 
more closely the movements of trains through interlocking 
plants where route and other locking is practiced. The informa- 
tion concerning the approach of trains is generally given by 
disc indicators; while that concerning the movements over 
track sections through interlocked territory is usually given by 
semaphore indicators. These are ordinarily located on the wall 
of the tower where they can be easily seen by towermen. 




CHAPTER X 



MANUAL BLOCK SYSTEM 

A manual block system is one in which the signals or other 
devices governing the spacing of trains are operated by hand. 

There are three ways of 
applying the system; Man- 
ual Block, Controlled- 
manual Block, and Electric 
Train Staff. 

THE MANUAL BLOCK 

123. General Description. 

The manual block is noth- 
ing more nor less than 
the ordinary telegraph or 
telephone block where an 
operator at one station is 
free to clear his signal at 
any time without electrical 
or mechanical check from 
any other station. Ad- 
jacent operators communi- 
cate by telegraph or 
telephone and clear or hold 
trains according to the rules 
in force on the particular 
road. The blocks are gen- 
erally the distance between 
ordinary commercial sta- 
tions, but occasionally on 
busy Hnes intermediate 
towers are built in order to 
shorten the blocks. The 

Fig. 199. — R. S. A. double-arm upper signals are given by train- 
quadrant train-order signal. i • i 

order boards, which stand 
in front of the station building or tower. One arm of the signal 
governs movements of trains in one direction and the other arm 
those in the opposite direction. 

186 




MANUAL BLOCK SYSTEM 187 

There are three roundels or glasses in each signal, and one 
lamp serves the purpose of all of them. Usually the signal 
indicates either stop or proceed, but a few roads use the 45-degree 
position for giving crews an indication for a 19 order. The posi- 
tions of the blades and the colors of the lights correspond to those 
in use for ordinary signaling purposes. Figure 199 is the type 
recommended by the Railway Signal Association and operates in 
the upper quadrant. 

The telegraph method of signaling has no check whatever on 
broken rails or open switches as some of the other methods have. 
Although the system is still in use on a great many branch lines 
and smaller roads, there are so many chances for accidents to 
trains through mistakes made by operators that other systems 
have been installed which have more checks to safeguard the 
train movements. 

THE CONTROLLED -MANUAL BLOCK 

124. General Description. — In the controlled-manual block sys- 
tem the signals are operated mechanically, but are so controlled 
electrically that the signal at one station cannot be cleared without 
the aid of the operator at an adjacent station. If operator A 
desires to clear his signal for an approaching train to pass into a 
block, he must communicate with the operator -B at the other end 
of that block, and request him to assist in releasing the lock on his 
signal mechanism. If B is in position to permit the train to 
enter the block, he compHes with the request, after which A may 
proceed to clear his signal. 

Figure 200 shows a form of controlled-manual machine made 
by the General Railway Signal Company. To move a train from 
A to B, the operator at A signals B by means of a bell to close the 
circuit at 3, Fig. 201, in his controller by turning arm 12. At 
the same time, A closes 10 by operating his lever 13. The circuit 
being then complete, current will flow from battery 28 through 
wire 1, contacts 2-2 of the lock L, contacts 3, wires 4 and 5, 
contacts 6, wire 7, indicator magnet 29, wire 8, indicator magnet 
30, wire 9, contacts 10, wire 11, electro-magnet 31, and to the 
ground. When magnet 31 becomes energized, the lock 14 is 
lifted and lever 15 may be withdrawn unlocking lever 19. When 
lever 19 is turned one-half a revolution the signal is cleared. It is 
restored to the stop position by completing the revolution. A 
ratchet wheel, 18, is provided to insure that the handle 19 be 



188 



RAILWAY SIGNALING 



turned only in one direction. The pipe that operates the signal 
is connected directly to the crank 21. There is a lug, 22, on the 





Fig. 200. — ControUed-manual station block instrument. 



^ 



^ 




FIG V 

Fig. 201. — Wiring diagram for controlled-manual system. 

ratchet wheel 18, that when the signal is returned almost to the 
stop position engages the arm 23 and forces the lock 17 into its 




MANUAL BLOCK SYSTEM 189 

seat requiring that the signal be again unlocked before it can be 
cleared. 

Besides being a check on the operators, there are different 
degrees of track protection afforded by the controlled-manual 
system where track circuits are installed. The length of the 
track circuit may be, in some cases, merely enough to protect 
switches and to control semi-automatic signals at each end of the 
block; while it may extend entirely through the block, in other 
cases, giving better protection against broken rails. The ordi- 
nary train-order boards are used where there are no track cir- 
cuits, and slotted signals where there are track circuits. A 
slotted, or semi-automatic signal, is one cleared by mechanical 
or other means, but is put to danger automatically by the train 
entering the block. These semi-automatic signals are equipped 
with electro-mechanical slots. 

THE ELECTRIC TRAIN STAFF 

125. General. — The staff system is one form of the controlled- 
manual system of block signaling and is applied only to single- 
track operation. The system finds its best application on roads 
with heavy traffic, being used principally in dangerous places, as 
at bridges and tunnels on non-electrified territory and at points 
where it is not feasible to install track-circuit signaling. The 
road is divided into blocks of 5 or 6 miles in length; usually the 
existing stations will suffice to form about the proper length of 
block when the staff system is installed, although occasionally an 
additional station will need to be supplied in order to expedite 
train movements. Two staff machines that are exactly alike 
are provided for each block, one stationed in the tower at each 
end of the block. The two machines are so connected by wires 
that they are interdependent in operation. 

The train is given a metal staff and this eliminates the necessity 
of a written train order. No train is allowed to proceed into a 
block unless the engineman has a staff. Only one staff can be 
taken out of either instrument at a time; and when one is out, 
both instruments are automatically locked and remain locked 
until that staff is returned to one or the other of the two machines. 
The engineman must take a new staff at the beginning of each 
block and deliver it at the end of that same block. The staffs 
are made of steel rods, % in. in diameter and 6 in. in length, so 
cut with such a series of annular grooves that those used in one 



190 



RAILWAY SIGNALING 



block will not fit the instruments of the adjacent blocks. The 
instruments are duplicated, but the distance between duplicate 
pairs is great enough to prevent the staffs from being carried 
over. 

126. Operation of the Absolute Staff Instrument. ^ — In the 
description of the staff equipment made by the Union Switch & 
Signal Company, a train is considered to move from station X to 
station Y, Fig. 202. The operator at X presses his bell key A the 
number of times prescribed in the bell code, and rings the bell L 
at F, Fig. 204, from the positive side of the battery through the 
circuit 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and re- 



y^MariTed Indicator 




Line 6--^ 
Fig. 202. — Wiring diagram for absolute train staff system. {Signal Dictionary.) 

turn to the battery. The operator at Y acknowledges the call 
by closing his bell key A, thereby ringing the bell L at X through 
the circuit 19, 20, 21, 8, 7, 6, 5, 4, 22, 23, 24, 25, 17, 16, 15, 14, 13, 
26; and as he continues to hold it closed, he deflects the ''current 
indicating needle," F, Fig, 203, at X to the right. Thus in- 
formed that Y has furnished the necessary current, X proceeds to 
remove the staff by turning the preliminary spindle handle Bj 
Fig. 203, to the right as far as it will go. This raises the armature 
J, Fig. 206 up to the magnets K, transferring the current from 
bell L to the magnet X-88 through the circuit 19, 20, 21, 8, 7, 6, 5, 
4, 22, 23, 27, 28, 25, 17, 16, 15, 14, 13, 26, and at the same time 
closing the circuit on magnet X'-360 through the circuit 1, 2, 29, 
1 From the Signal Dictionary, p. 38. 



MANUAL BLOCK SYSTEM 



191 



30, 28, 25, after which the preHminary spindle handle is permitted 
automatically to return to its normal position. This unlocks 
the revolving drum, C, Fig. 206, and indicates the fact by dis- 
playing a white instead of a red disc in the indicator, H, Fig. 205. 
The operator now moves the end staff, E, Fig. 203, up the vertical 
slot into engagement with the drum, C, Fig. 206, (the outer guard, 
N, Fig. 205, having first been turned to the right position), re- 
volves the latter through a half turn, using the staff as a handle, 





Fig. 



203.— Absolute staff 
instrument. 



Fig. 



204. — Rear view of absolute 
staff instrument. 



and finally withdraws the staff through the opening at M, Fig. 
203. In making the half turn, the drum, C, Fig. 206, has re- 
versed the polarity of the operating current, thereby throwing the 
instruments at X and Y out of synchronism with each other and 
moving the ''staff indicating needle," G, at X, Fig. 207 from 
''Staff In" to "Staff Out." Immediately on withdrawing the 
staff, the operator at X once more presses his bell key A, which 
indicates to the operator at F, by moving his needle from "Staff 
In" to "Staff Out" that the operation is completed. He then 
prepares to deliver the staff to the train. 



192 



RAIL}VAY SIGNALING 



The magnet K, Fig. 202 has two separate coils, X-360 energized 
by the local battery and K-SS energized by the line battery. 
The polarity of the current through K-360 is never changed, 
but that through Z-88 is changed every time a staff is put in or 
taken out of either instrument. When the currents in both coils 
have the same polarity, there is no attraction for the armature. 








Fig. 205, — Front view of staff instrument in con- 
dition for removal of staff. 



Fig. 206.— Staff Instrument 
with armature up. 



When the current is reversed in one coil, the lines of force oppose 
each other and the armature being brought to the point of attrac- 
tion, is held there. With the staff out, if an attempt should be 
made to release another staff by turning the preliminary handle, 
the circuit closed would be from the positive side of the battery 
through 19, 20, 21, bell key A closed, 8, 7, 6, 5, 17, 25, 28, 27, 
23, 22, 4, 16, 15, 14, 13, 26, to the negative side of the battery 



MANUAL BLOCK SYSTEM 



193 



at Y, with the polarity of the current flowing through magnet 
K-S8 reversed. By comparing this circuit with the one des- 
cribed for releasing the staff it will be seen that in the former 
the currents flowing through magnets K-SQO and K-SS oppose 
each other, and in the latter they do not, which prevents the 
releasing of the second staff. 





Fig. 207. — Front view when a staff is released or 
about to be replaced. 



Fig. 208.— Side elevation 
of staff machine. 



On arrival of the train at Y the crew delivers the staff to 
the operator, who places it in the opening M, Fig. 203, of his 
instrument, having first turned the outer guard, N, Fig. 205, 
to place. He moves the staff into engagement with the drum D, 
Fig. 206, revolves the drum through one-half turn to the right, 
using the staff as a handle, and allows the staff to roll down the 
spiral. He then presses his bell key the prescribed number of 

13 



194 



RAILWAY SIGNALING 



times, thus notifying X that the train is out of the section, which 
operation also moves the ''staff indicating needle" at X from 
''Staff Out" to "Staff In." The operator at X presses his bell 
key in acknowledgment, and by so doing moves the "staff indi- 
cating needle" at Y from "Staff Out" to "Staff In." The 
machines are now synchronized and another staff can be obtained 
from either in the manner outlined above. 

If the speed of the train does not exceed 25 miles an hour, 
the staffs removed from the instruments by the block operators 
are delivered to the enginemen by hand by means of a small hoop 




Fig. 209. — Staff catcher and deliverer. 



formed of a piece of rubber hose. If the speed is more than 25 
miles an hour, they are delivered by means of a staff catcher that 
operates something on the order of a mail crane, as shown in Fig. 
209. The staffs are returned to the operators in a similar manner. 
127. The Permissive Staff. — Where several trains are allowed 
to follow one another at short intervals through the block, they 
operate under what is termed the permissive system. A permis- 
sive attachment, shown in Fig. 210, is installed at each end of 
each block in connection with the absolute machine with only 
one permissive staff for the two instruments. To move a series 
of trains from X to F this staff must be at X. The permissive 
staff, represented by Fig. 211^, is made by passing a double 
steel rod through 11 separate and removable discs, called tablets. 



MANUAL BLOCK SYSTEM 



195 



There is an additional disc fastened to the end of the rod making 
altogether 12 separate pieces in the staff. To operate the 
machine one of the regular staffs used in the absolute system is 
removed from the instrument at X and is used to unlock the 
permissive attachment. The withdrawal of the permissive 
staff locks the absolute staff in the permissive case and it cannot 
be removed until the permissive staff is returned to the case at 
one end or the other of the block. 




^ /-J-— -->i k— /V-">i 

Fig. 210. — Permissive and pusher attachments. 



As the trains enter the block, each one except the last takes 
one tablet, thus providing that as many as 12 trains may go in 
one direction should there not be occasion in the meantime to 
send one in the opposite direction. If there should be less 
than 12, the last one would take all that is left of the staff 
including the steel rod. These pieces are all delivered by the 
trains to the operator at Y, the leaving end of the block. He 
assembles them again into a single unit and places them in his 
permissive attachment. This allows the absolute staff to be 
released; and as soon as it is returned to the absolute machine, 
an absolute staff may be removed at either end of the block. A 
train may now move in either direction with an absolute staff 



196 



RAILWAY SIGNALING 



and from F to Z with the permissive staff. If it is anticipated 
that another series of trains will move from X to F, the first 
engineman going from F to Z will use the permissive staff 
instead of an absolute, for the permissive staff, as a whole, con- 
fers the same rights as an absolute staff. The operator at X will 
then be prepared to handle the trains by the permissive system. 
An engineman having any part of the permissive staff is certain 




— 1 (-■ 

._) L_. 



1 ^ o 




E t 






DItlps© 



mtnn 



©4^n:^\^mmmfi E 



Fig. 211. — Staffs and staff pouches. 

that he will not meet a train, but he will expect to find one 
preceding him unless he has the first tablet, or one following 
him unless he has the rod and possibly some remaining tablets. 
128. Intermediate Siding and Junction Instruments. — At 
sidings between stations a special staff machine may be installed 
to govern movements of trains that meet there. If there is a 
train to leave X for the siding between X and Y, the operator at 
F will unlock the instrument at X and allow a staff to be removed. 
This staff is handed to the engineman and when the train arrives 



ii 



MANUAL BLOCK SYSTEM 197 

at the siding the staff is used to unlock the switch. After the 
train is entirely in the clear on the siding and the switch is locked, 
the staff is placed in the special staff instrument there, synchron- 
izing the instruments at X and Y. 

If there is a junction point between the two stations X and Y, 
a special junction instrument is often installed there when there 
is not enough traffic on the branch line to warrant a com- 
plete station and set of instruments. The movements from 
the point X or F to the junction and into the branch line are 
made just as are those explained above. 

When a train is to leave a branch line or siding for the main 
line, the crew calls both X and Y. The operators at these two 
stations acting together can release a staff in the junction or 
switch instrument. When this is removed every machine in that 
block is locked and remains so until the staff is returned to any 
one of them. After the crew unlocks the switch with this staff, 
the train pulls out on the main track. The crew locks the switch 
again and takes the staff to X or Y, depending upon the direction 
they are traveling. 

129. Pusher Attachment. — In order to operate a pusher 
engine a portion of the distance between X and Y and let it 
return to X, a special pusher engine instrument is attached to 
the absolute instrument, Fig. 210. The pusher staff can be 
released only by a staff from the absolute machine. Both 
staffs, however, can be removed at one time. In order to proceed 
from X to Y, the operator at X signals Y to release the absolute 
staff. X removes this staff and uses it to unlock the pusher 
staff. The train takes the absolute staff and the pusher engine 
the pusher staff. After the pusher engine has gone as far as 
necessity requires, it returns to X while the train goes on to Y. 
Both deliver their staffs, the one at X and the other at Y. No 
other staff can be removed from either end of the block until they 
both are returned. In Fig. 211, numbers 1, 2, 3, and 4 represent 
absolute staffs and 5, 6, 7, and 8 represent pusher staffs. 



CHAPTER XI 
AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 

GENERAL 

130. Object. — The purpose of automatic block signaling on 
double track is to provide automatically by the trains themselves 
such an interval between trains moving in the same direction 
over the same route as will secure safety and efficiency in opera- 
tion. One of the factors that influence the efficiency of a block 
system is the length of its blocks. The manual and controlled- 
manual systems, where the length of block varies from 3 to 8 miles, 
provide for only one train between stations or towers, for there 
can be only one train in a block at one time. The automatic 
block system, where the average length of block is practically a 
mile, is much more effective. It permits a shorter interval 
between trains and an additional factor of safety. Closing a 
station or tower at night has the effect of rendering the manual 
system still more inefficient, but has no effect on the operation of 
the automatic system. By using automatic block signals, the 
trains can in many cases, operate without train orders. This 
tends to eliminate some of the expense of having operators to 
deliver the orders and of stopping and starting trains to receive 
them. The same analysis of the cost of starting and stopping 
trains could be made for automatic signals as for interlocking. 

Running trains over a division in a shorter time will not 
only curtail the overtime wage for train crews, but will also 
give a more intense service for the train equipment. The same 
number of engines and cars will handle more business in an equal 
length of time. The detection of broken rails by means of 
track circuits is an item of great advantage. 

Of the 99,360 miles of block signals installed in the United 
States up to 1919, 36,600 were automatic. In order to install a 
system of automatic block signals on single or double track, the 
road is divided into blocks varying in length from a few hundred 
feet to a few miles, depending upon the length of trains and the 
amount of traffic handled. The trains operate these automatic 
block signals by means of electric current flowing through the 
rails and through wires running along the right-of-way. 

198 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 199 

131. Location of Signals. — There are several factors that 
influence the spacing and location of automatic block signals. 
Whatever the kind of train service the road is giving, the spacing 
between the home and distant signals should exceed somewhat 
the maximum braking distance for the highest speed attained in 
that block. Since it is one of the functions of block signals to 
expedite train movements, the blocks on roads having dense 
traffic should necessarily be shorter than on those having light 
traffic. As trains run faster on down grades than on up grades, 
the blocks should be longer going down. Trains should be able 
to cover blocks in about equal spaces of time. Signals should be 
so placed as not to stop tonnage trains on heavy grades, if possi- 
ble; for when they stop they will generally experience some 
difficulty in starting again. In terminals where trains are 
frequent, but where their movements are slow, the blocks should 
be shorter than they are in the open country. Signals should 
stand as near the beginning of curves as practicable in order to 
give the enginemen a chance to see them as far as possible. It is 
much easier to see them against an open-sky background than 
against trees or buildings or the side of an open cut. They 
should, however, stand in front of bridges, water-tanks, and 
tunnels and not immediately behind them. A signal near a 
station should stand beyond the depot where the engineman can 
see it when he makes the station stop. In such cases he would 
ordinarily not start his train until the signal should go to the 
proceed position. 

From an article entitled ^'Automatic Signal Locations," by 
the late C. C. Rosenberg, and published in Volume II of the Pro- 
ceedings of the Railway Signal Association, the following para- 
graphs have been selected: 

''In making a survey for the installation of automatic signals, one of 
the greatest problems to be solved is that of location, and in order to 
get the best results, it is necessary that the subject be given careful 
study and thorough consideration from every standpoint. 

"Signal Engineers and others in charge of signal construction on 
roads which have automatic signals, find that after signals are placed in 
service, some are to a great extent of little value owing to poor sight, 
stalling of trains, etc., and in some instances give confusing indications. 
In order to correct these, considerable expense is incurred which could 
to a large extent have been avoided if proper consideration had been 
given at the time of locating. 



200 RAILWAY SIGNALING 

"In locating, the following conditions should be considered; the 
relative relation of the signal to sight, passing sidings, crossovers, 
interlocking plants, junction points, passenger stations and length of 
block. 

''As all railroads are not fortunate enough to have long tangents, it is 
often a serious problem to get a good sight for a location on account of 
obstructions or being placed in a series of short curves ; it is often neces- 
sary to lengthen or shorten the block in order to get even a fair sight. 

"At a passing siding, the signal should be placed back of the fouling 
point of the outlet switch, so as to protect a train moving from the 
siding to the main track; while at the same time allow an approaching 
train on main track to advance one block farther than if placed ahead of 
the switch. No signal should be placed immediately ahead of an outlet 
switch, and used as a starting signal; but in order to give a train moving 
from a passing siding a starting signal, it should be placed at a distance 
far enough in advance of the outlet that it cannot be mistaken by a 
train approaching on the main track as its signal. The train moving 
from the siding to the main track should proceed cautiously and under 
full control until the next signal is reached. The proper location for a 
signal at the inlet of a passing siding is within 500 ft. of the switch 
points, and the next signal in rear should be placed not more than ^i 
mile from the switch, preferaby less, if it can so be arranged. 

"No location should be made immediately in advance of a crossover, 
but far enough in the rear to protect the same should the location be 
found to come in the vicinity of such crossover. 

"Locating signals on the outside of curves should be avoided as far 
as possible ; but if this is found necessary, then the masts should be high 
enough to place the signals so that they can be seen from approaching 
trains over the top of a train passing in the opposite direction, or a train 
standing on a siding. 

"Telegraph pole lines should, wherever practicable, be moved as 
near the right-of-way as possible so as not to obstruct the sight of 
signals. All undergrowth and overhanging trees should be kept trim- 
med, so that a good view can always be obtained. 

"In order to give extra protection to trains handling freight and 
passengers at stations, a signal should be located from one thousand to 
twelve hundred feet on either side of the station; this will allow an 
approaching train to advance, and often avoid making a stop at the 
signal in rear, should a train be standing within station limits. 

"The length of block must be determined by traffic and track condi- 
tions. Where the traffic is not very heavy and the road bed practically 
level and not more than 0.5 per cent, grade, 1-mile blocks are considered 
very good practice. If traffic is congested this distance should be 
reduced to from H to ^ mile. On approaching ascending grades over 
0.5 per cent., blocks should be gradually shortened until a uniform length 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 201 

can be maintained; this should be done in order to avoid any unneces- 
sary stops for following trains. On descending grades, blocks can be 
lengthened to conform to traffic and grade. In territory comparatively 
level and where traffic is not congested, IK- to 2-mile blocks can be 
successfully operated. 

''No location of a signal should be made just beyond a sag or apex, 
as a train obhged to stop at such a signal is likely to break in two in 
starting. 

"Before making a final survey it is well to consult with the engineering 
and traffic departments relative to track changes, such as changing 
locations of crossovers and siding switches, and in some cases present 
sidings may be eliminated, thereby saving considerable expense if these 
changes can be made before signal work is begun. 

"After locations have been made and considered from a signaling 
standpoint, the transportation department should be consulted, and 
the ground thoroughly canvassed, so as to determine definitely that the 
signals as located can be successfully operated from a traffic standpoint. 
It is also a good plan to get the views of competent enginemen as to 
locations, and ascertain from them if any are in localities liable to cause 
trouble. 

"In some foreign countries, the practice of locating signals for sight, 
is to use a full-sized templet of a mast and blade and send out a locating 
party. After a sight has been selected, the templet is placed in position 
and viewed from an approaching train. If not seen to a good advantage, 
the templet is moved from place to place until the best sight is obtained; 
this accomplished for day signals, the same process is followed at night, 
except that a light is placed on the mast instead of the blade. Very 
frequently, in making both night and day tests, it is found that the 
location which gives the best sight for a day signal may not answer for a 
night signal, which necessitates the selection of a new location. While 
this method may at first glance seem to be unnecessary, it is certainly 
well worth considering." 

132. Two-position Semaphore Signaling. — Where the blocks 
are rather long, the home and distant signal arms are sometimes 

Trar/h 



IP /// 3D 3H SP SH 

Fig. 212. — One-arm two-position signals. 

mounted on separate posts, as shown in Fig. 212. These signals 
give only two indications, stop or caution, and proceed. The 
home signal stands at the beginning of the block and governs 
movements into the block. The distant signal, serving purely a 



202 RAILWAY SIGNALING 

cautionary function, stands from 2,000 to 4,000 ft. in the rear and 
simply repeats the indications of the home signal. The train has 
caused the home signal 3^, to go to the stop position, and it, in 
turn, has caused distant signal SD to remain in the caution posi- 
tion. Both signals will keep these positions until the train 

^ ! -.IZIZIl ! ' : ■ ! . 

Fig. 213. — Two-arm two-position signals. 

passes the next home signal, when they will both go to the pro- 
ceed position again. 

Where the blocks are shortened, the home and distant signals 
are usually placed on one mast, as shown in Fig. 213. In this 
case, the home signal governs not only the first distant signal in 
the rear, but also the one on its own mast. In the case of a four- 

/?/». /?/» /^ /^ n f1 />M 

.^ /?/y\ ; iLiiJ ' .^2KJ ;^^ />/» I ' />/yr — ; 



/ 

Fig. 214. — Two-position bracket post signals on a four track line. 

track line, the signals are frequently mounted on the bracket type 
of post in a manner such as is indicated in Fig. 214. The inner 
signals govern track No. 1 and the outer ones track No. 2. 

133. Three -position Signaling. — The three-position signal is a 
step in advance of the two-position, for it combines the home and 
distant signal in one, thereby saving about half of the posts. 



Js 



I l> 



^ ^ I T 

Fig. 215. — Three-position lower and upper quadrant signals. 

motors, and lights. This reduces not only the rather serious first 
cost in the matter of construction, but also the heavy expense of 
maintanence. The 45-degree position signal 3, Fig. 215, indi- 
cates that there is a train in the block immediately in front of the 
one it governs, and warns enginemen to be prepared to stop when 
they reach the beginning of that block. 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 203 

134. Overlap Systems. — As a measure of protection an over- 
lap system was devised whereby a signal did not go to clear until 
the train had advanced a certain distance beyond the next home 
signal, the idea being to keep one full block and a portion of an- 
other between two trains going in the same direction. In Fig. 
216 a train in section A of block 3 holds the home and distant 

K- B/i^cA/- ->j<-- BI(Pck2- ^--—- Block 3 ^ 

; ! !!'! I tv I y =^ 

Fig. 216. — Partial block overlap. 

signals at the beginning of block 2 in the stop and caution posi- 
tions, but when it passes from section A into section B it allows 
the home signal to go to the proceed position. 

This system is often criticised on the ground that as there are 
times when there are two home signals standing in the stop posi- 
tion between one train and another one following it as closely as 



Fig. 217. — Full block overlap. 

the signals will permit, the enginemen may on some occasions be 
inclined to pass one of these signals at high speed. 

In some cases where the blocks are short, as in the New York 
Subway, a full block overlap has been provided in order to secure 
additional protection. In this case two full blocks are between 
two trains going in the same direction, as indicated in Fig. 217. 

135. Absolute and Permissive Signaling on Double Track. — 
The common practice in double-track automatic block signaling 
on many roads is for a train to stop at a home signal that shows a 
stop indication, then after waiting one minute proceed at such a 
low speed as to be able to stop at any time. The stop indication 
may be due not to a train in the block, but to a break in the rail 
or to an obstruction on the track or to some failure of the signal 
apparatus; and if there should not be some method of procedure 
in such instances, traffic would be seriously delayed. Some roads 
require that a flagman proceed the train into the block in such 
cases to warn it of the danger. This plan of allowing one train 
to follow another into a block without receiving the proper indi- 
cation from the home signal to do so is called permissive signaling. 
Many roads distinguish between absolute (stop and stay) and 



204 



RAILWAY SIGNALING 



permissive (stop and proceed) signals by making the blades of the 
absolute home signals with square ends and those of the permis- 
sive with pointed ends, as shown in Fig. 218 and Fig. 219. 




Fig. 218. — Absolute signal. (Hall Switch and Signal Co.) 



The night indications as to whether a signal is absolute or 
permissive is shown by the position of the lamp, called a marker, 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 205 

fastened to the signal post some distance below the signal lamp. 
A marker placed directly below the signal lamp, on the same side 
of the post, indicates an absolute signal; and on the opposite side 




Fig. 219. — Permissive signal. {Hall Switch and Signal Co.) 

of the post, a permissive signal. A marker may be either a red or a 
yellow light. All home signals at interlocking plants are absolute. 



206 



RAILWAY SIGNALING 



136. Three-block Indication Scheme. — Some roads have 
adopted the idea of using two-arm signals for giving information 
to trains as outlined in Fig. 220. The blades are made with 
pointed ends and operate in the upper quadrant. In the case 
of the upper blade, the signal light is on the right-hand of side of 



1. stop, then proceed. 



K? 



2. Proceed prepared to stop at 
next signal. 



3. Proceed prepared to pass 
next signal at medium 
speed. 



4. Proceed. 






II 



Fig. 220. — Three-block indication scheme. 

the post and in the case of the lower one, on the left-hand side to 
act as a permissive marker. This combination of signals affords 
a much wider range of indications, the same really as would be 
displayed by a four-position signal, and is used to give indica- 
tions for three blocks instead of two, as is ordinarily done in 



n n 



^5^ 



q n 



B C P 

Fig. 221. — Three-block indications. 



practice. A train in block A will cause the signal to display 
indications as shown in Fig. 221. 

137. Numbering Automatic Signal Posts. — All automatic sig- 
nal posts should be numbered, the even numbers governing trains 
going in one direction and the odd numbers those in the opposite 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 207 

direction. There are two ways of designating them, one is to 
number them consecutively through the mile, and the other to 
use the nearest even or odd tenth of mile in addition to the mile- 
post number. By the first method, the signals running in one 
direction between mile posts 264 and 265 would be 2642, 2644, 
and so on if there should be more than two ; and in the other direc- 
tion 2641, 2643, and so on. By the other method the numbers 
would be, for example, 2646 for trains in one direction and 2649 
for those in the other, depending upon the particular location 
that the signals should occupy in that mile. Branch lines may 
be numbered by a prefix letter, as X2641 and X2643. Figure 
219 shows the method of numbering main fine posts. Inter- 
locking signals do not bear numbers except the distant signal used 
in connection with three-position automatic block signals. 



CHAPTER XII 

AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 
DIRECT-CURRENT TRACK CIRCUITS 



NORMAL CLEAR SIGNALS 

138. Two-position Signal Circuits. — Figure 222 shows the 
wiring for two-position signals on double track where the home 
and distant signals are on separate posts. The home signal has a 
very simple motor control circuit. The distant signal is controlled 
by the front contact of a neutral relay for a train in its immedi- 
ate section, and by a line relay and circuit breaker operated by 
the home signal for a train in the home signal section. A train in 
block C will deenergize its relay and cause signal H-d to go to the 
stop position. The circuit breaker C-3 will then be opened, 
breaking the circuit to S-S, dropping its armature and allowing 



■//-/ 









m 



-//-J 



&i 



Common Wire-,, 



C-. 



^/T 



DisfanfSiffnal Conj-rolWire* 



£ 



Fig. 222. — Wiring diagram for one-arm two-position signals. 

Z)-3 to go to the caution position. By means of the cut section, 
signal U-X will remain in the stop position while the train is in 
section B. 

Figure 223 shows a series of two position automatic block 
signals on double track where the home and distant signals are 
on the same post. The home signal governs the distant signal on 
the same post, and also the one in the rear by means of circuit 
breakers. A train in block C shunts its track relay allowing the 
home and distant signals 5 to go to the stop and caution positions. 
As there is no train in block 5, home signal 3 goes to the proceed 
position, but distant signal 3 remains in the caution position 

208 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 209 

held there by the circuit breaker C-5. The circuit that energizes 
S-S, the control relay of distant signal 3, is from battery, through 
second contact of track relay 5, circuit breaker C-5, relay S-3, and 
common return to battery. When this circuit is broken by cir- 
cuit breaker C-5, the relay ^-3 is deenergized breaking the front 




Fig. 223. 



Common Wire '■'^ 
Two-arm two-position signal circuits. 



contact to the distant signal 3. Both signals in block A are 
clear because the circuit breaker C-3 is closed. 

Figure 224 represents a wiring diagram for two-arm two-posi- 
tion signals prepared by Committee IV of the Railway Signal 
Association and printed in the 1910 issue of the Proceedings.^ 




Fig. 224.- 



//- //ome Confro/ Pehy 
D - D/S/orrf ■• 

-R. S. A. circuits for two-arm two-position signals. 
1076A, page 367, Proceedings 1910.) 



(Plan No. 



139. Two-position Polarized Track Circuits. — Figure 225 
shows the plan for polarized track circuits for two-position signals 
where the home and distant signals are on separate posts. A 
train in block C will drop the armature and break the circuit to 
home signal 3. As it goes from the clear to the stop position, it 
shifts the pole changer, which in turn changes the direction of the 
track current in section B. This repels the polarized armature P 

1 Page 367. 
H 



210 



RAILWAY SIGNALING 



and breaks the circuit to distant signal 2 allowing it to remain in 
the caution position. As home signal 1 is controlled only by a 
neutral relay, it will take the proceed position. This plan is used 
only where the traffic is light and the blocks are long, too long for 
a distant signal to be a full block from its governing home signal. 
Figure 226 shows the Union plan for normal clear polarized 
track circuits and two-position signals on the same post. In 
addition to the pole-changer, there is a circuit breaker operated by 




IM 



J— 'v 



'\m 



Fig. 225. — Polarized track circuits for one-arm two-position signals. 

each home signal. The home signal is connected directly in cir- 
cuit with the battery and neutral contact of the relay. The 
distant signal is in circuit with the battery and neutral contact of 
the neutral relay and also with the polarized contact of the 
relay. The distant signal is thus controlled entirely by the home 
signal. Whenever a train enters a block it shunts the relay and 
allows the home signal to go to stop, thereby breaking the 
circuit to the distant signal on the same post setting it to caution. 




1 











Fig. 226. — Polarized track circuits for two-arm two-position signals. 

When the home signal is horizontal, it manipulates the pole- 
changer so as to send the current in one direction; when it is in 
the proceed position it causes the current to flow in the opposite 
direction. When the home signal goes to the proceed position 
the circuit is made through the polarized armature in the rear 
and the distant signal there goes to clear. 

In the sketch, the train is deenergizing the first track relay in 
the rear and holding the signal in the stop position. In order that 
the home signal may not momentarily tend to drop the stop 
position while the pole-changer breaks the track circuit, shifting 



Ji 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 211 



from one contact to the other, a slow releasing magnet is fre- 
quently employed. 

Figure 227 represents typical circuits for two-arm two-position 
polarized track circuits, while Fig. 228 represents typical circuits 
for two-arm two-position polarized line circuits. ^ 




Fig. 227. 



-R. S. A. two-arm two-position signals, polarized track circuits. 
(Plan No. 1077A, Page 368, Proceedings 1910.) 



140. Three-position Signal Circuits. — A sketch of the General 
Railway Signal wiring plan for three-position signals is shown 
in Fig. 229. The 45-degree position of signal 1 is controlled by 
a circuit through its local battery, third and fourth contacts of 
the track relay, and the common return. The 90-degree position 
is controlled by the circuit breaker and the battery of the signal 
in advance. If the block that is governed by signal 3 is occupied 




^^^^-'K^^^isp'''''^^ 



CH 



<|||'I<I'M 



i 



Fig. 228. 



-R. S. A. diagram for two-arm two-position signals. Polarized line 
circuits. (Plan 1078A, page 369, Proceedings 1910.) 



by a train, its relay is deenergized and signal 3 goes to the stop 
position. As the block that is governed by signal 1 is not occup- 
ied, its relay becomes energized and signal 1 goes to the 45-degree 
position. As the train moves one block to the right, signal 3 goes to 
the 45-degree position and signal 1 goes to the 90-degree position 
because the 90-degree relay at signal 1 becomes energized from 
the battery at signal 3. 

1 Proceedings Railway Signal Association, pages 368 and 369, Volume 1910, 



212 



RAILWAY SIGNALING 





ii 



J 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 213 



141. Three-position Polarized Track Circuits. — Figure 230 
shows the Union design for 
a three-position signal system 
operated by polarized track 
circuits. The 45-degree po- 
sition is controlled by the 
neutral contacts and the 90- 
degree position by the polar- 
ized contacts. 

NORMAL DANGER SIGNALS 

142. Two -position Signal 
Circuits. — Normal danger 
signals are those that stand 
normally at stop when the 
track is not occupied, but 
which go to the proceed 
position upon the approach 
of a train. They assume the 
stop position again as soon 
as the train enters the block 
they govern. 

Figure 231 is plan 1,079 A 
printed in the 1910 issue of 
the Proceedings of the Rail- 
way Signal Association, with 
some additional lettering to 
aid in explanation, and rep- 
resents a two-arm two-posi- 
tion normal danger system. 
When a train enters the last 
section of block A, distant 
signal 3 and home signal 5 go 
to clear provided there is no 
train in either block B or C. 
The circuit for clearing these 
two signals is battery at signal 
7, second contact of relay C-5, 
first contact relay T-5, relay 
H, relay A, middle circuit 
breaker at signal 3 closed by home signal 3 cleared, relay D, back 




214 RAILWAY SIGNALING 

side fourth contact on relay C-1, and common return to battery 
at signal 7. 

When the train enters block B, the home signal 3 goes to 
stop because the circuit is broken by the track relay. This, in 
turn, opens the middle circuit breaker operated by home signal 3 
and allows the distant signal 3 to go to caution. Home signal 5 
remains at clear, for the current has another route through the 
back side of the third contact of relay C-S and through the 
resistance to the common wire. Home signal 7 and distant 
signal 5 go to clear when the train enters the last section of 
block B, 

The function of relay A is to allow relay H to pick up first, 
clearing home signal 5 before relay D can pick up to clear the 
distant arm of signal 3. 

SWITCH, CURVE, AND SIDING PROTECTION 

143. Switch Indicators. — When the movements of a train are 
controlled by automatic block signals, switch indicators, as shown 
in Fig. 167, are usually provided at the switches, especially those 
in outlying districts. The indications may be either visible or 
audible, and are to inform a switchman whether or not a train is 
approaching, so that he can be governed intelligently concerning 
the opening of the switch. Visible signals are either miniature discs 
or semaphore arms actuated by electro-magnets energized by line 
wire circuits that extend through at least two full blocks in the 
rear of the switch. These wires are connected through the nor- 
mally closed contacts of all the track relays or home signal arms 
in those two blocks so that the approach of a train will break the 
circuit and allow the indicator to come to stop. Thus the 
switchmen receive a warning that a train is immediately approach- 
ing and will not open the switch until the train has passed. The 
indicator is enclosed in an iron case with a glass front, and is 
placed in such a position near the switch stand that it can be 
easily seen by switchmen. 

The audible warning is given by a bell placed in the immediate 
vicinity of the switch. The wiring for the bells is practically the 
same as it is for the visible indicators. In either case the wiring 
should extend back far enough so that the warning should occur, 
at least, by the time the train approaches the distant signal con- 
trolled by the first home signal in the rear of the switch. 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 215 



144. Switch Box. — ^Located at each switch in a track with 
automatic block signals is a switch circuit controller, Fig. 232, so 




Fig. 232. — Switch circuit controller. 



connected to the switch points by a rod that when the switch is 
open the circuit through the switch box is closed. They are 




® 



Common 

Fig. 233. — R. S. A, circuits for protection of facing switches. (Plan 1312.) 

generally made with four contacts not all of which may be used at 
one time. The switch box is usually arranged to shunt the track 




Fig. 234. 



/4(pf(^ for Normal 9cfng<?i 

Omit V }} jj I ' I ' t- 

-R. S. A. design for protecting obscure curves and switches. 
{Plan 1075A, vage 366, Proceedings 1910.) 



circuit, although sometimes it is placed in the circuit that con- 
trols, at least, the first home signal in the rear, so that when the 
switch is open the home signal will give the stop indication. 



216 



RAILWAY SIGNALING 



145. Signals for Outlying Switches and Obscure Curves. — 

Where the automatic block system is not in use, signals are some- 
times installed to protect trains at outlying facing point switches 
and on abscure curves where the view is somewhat obstructed. 
In the case of the switch, the signal may be mechanically operated 
by wires connected directly to the switch mechanism or it may be 
operated by power, the Railway Signal Association diagram of 




Fig. 



235. — R. S. A. normal clear circuits for trailing switch and curve protection. 
Traffic in one direction. (Plan 1074A, page 365, Proceedings 1910.) 



which is shown in Fig. 233. In this plan there are two block 
sections with independent track circuits, either one of which when 
occupied by a train will set the switch indicator to stop. 
When the switch is opened, or when the block in which it is located 
is occupied by a train, the signal will be placed in the stop posi- 
tion automatically. Figure 234 represents the Railway Signal 
Association circuit plan for protecting obscure curves and sidings. 



CHAPTER XIII 
AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 
ALTERNATING CURRENT 

146. Introductory. — Alternating current is used for signaling 
purposes on electric lines whether the propulsion current be 
direct current or alternating. In the case of direct-current pro- 
pulsion any commercial frequency of cycles may be used for the 
signal current, but in the case where alternating-current propul- 
sion is used, the two cycles must be different. The signaling 
current is entirely independent of the propulsion current. It is 
obtained from a substation, is carried along the right-of-way on a 
separate set of poles, and has its voltage stepped down by means 
of transformers. As it is used for operating both track circuits and 
signals, it has the advantage of eliminating the expense of bat- 
teries, and of battery wells and battery chutes. It serves to 
avoid, also, the difficulties that arise from foreign currents 
carried by the rails. To a certain extent it eliminates the cut 
section so commonly used in direct-current signaling, for in 
many cases the track circuit can be made as long as the block. 
The current can be used, also, for lighting the signals, switches, 
stations and other buildings along the line. Furthermore, there 
is not so much chance of signal failure in unfavorable weather 
because of the greater amount of power available for such pur- 
poses. It does require, however, a constant generation of current 
and the additional set of poles for transmission. Should the 
transmission line fail at any place, that part of the system would 
go out of service that should lie beyond the point of failure unless 
power should be supplied from some other source. The first cost 
of installing alternating-current equipment is generally heavier 
than that for direct current. 

On account of fewer complications in line construction, single- 
phase transmission is generally used in preference to three-phase 
where the current is not too heavy or the length of line too great. 
Voltages of 1,100, 2,200, 3,300, and 4,400 are being transmitted for 
signaling purposes. The higher the voltage the less copper 
necessary for the transmission service; but at the same time, the 

217 



218 



RAILWAY SIGNALING 



high-voltage current requires more expensive auxiliary equip- 
ment, such as transformers and lightning arresters. Single- 
phase current also eliminates the difficulties that arise from an 
unequal distribution of the current in the three wires in the case of 
three-phase transmission. ^ 

SINGLE-RAIL RETURN2 

147. Direct-current Propulsion. — There are two systems in 
practice where electricity is used for propulsion and where alter- 
nating current is used for signaling, the single-rail return and the 
double-rail return. The single-rail return can be used only where 
the return propulsion current is light enough to be carried by one 
rail and where it is not necessary to guard against broken rails, 
as in yards where train movements are slow. The double-rail 



F, 



7?f 






A^v^^^^^^ 



Fig. 236. — Single-rail return system. 

return requires more track equipment, which makes that system 
less desirable in yards and busy terminals. In the single-rail 
return system one rail is divided into blocks, as shown in Fig. 236, 
to operate the signal, and the other is left intact to act as a return 
for the propulsion current. It also serves to complete the track 
circuit. 

In practice when the block is not occupied or when the train 
is in the middle of the block almost all of the return propulsion 
current flows through the one rail and there is a drop in the poten- 
tial between the two rails at each end of the block depending upon 
the amount of resistance inserted at each place, the resistance of 

^ Page 90, Proceedings Railway Signal Association, 1917. 
2 From a paper by W. K. Howe, Proceedings, Railway Signal Association, 
Page 130, 1909. 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 219 

the rail and the amount of propulsion current in the continuous 
rail. When the train is entering or leaving the block, there is a 
tendency for a greater portion of the propulsion current to go 
through the block rail. In the first case, when the block is not 
occupied, there would be a tendency for some of the current to 
flow from the return rail through the relay at one end of the block 
and through the block rail to the secondary coils of the track 
transformer at the other end and to the return rail again. In 
the second case there would be the tendency for a greater portion 
of the propulsion current to go through the track transformer 
when the train enters the block and to flow through the relay 
when it leaves the block. This would magnetize the iron of the 





H 


1 




IH 




1 


y 




HIIIL 


M 


■r 




llnfluH 


iill 


li 


1 


wiB 




mIIIIIIIiI 


iiiinii 


1 


1..^ 


''^"'i 1^ 




mi 


JIUp*' 


M 


yi 


im 



Fig. 237. — Cast iron resistance grid. 



relay and transformers to such an extent as to interfere with the 
operation of the signal current. To eliminate this element of 
interference, two non-inductive resistances R and Ri are inserted 
in the track circuit, the one at the relay and the other at the 
track transformer. Where the blocks are only 200 or 300 ft. 
long and the current is comparatively light, tube resistances are 
sufficient, but where the blocks are 800 or 900 ft. long and the 
current correspondingly heavy, cast-iron grids, such as shown in 
Fig. 237, are employed. These resistances are high and the 
voltage of the track current will need to be proportionally high 
to drive the current through them. This will lead to a consider- 
able waste of current by leakage between the two rails with a 
corresponding drop in voltage varying with the initial voltage, 
length of block, and the ballast and track conditions. This 



220 



RAILWAY SIGNALING 



type of construction can be used economically only in cases where 
the difference in the pressure of the propulsion current in the con- 
tinuous rail at the two ends of the block does not exceed 15 volts. 
Such a drop would be equivalent to that from a current of 1,500 
amp. in 1,000 ft. of ordinary 80-lb. rail. If the difference exceeds 
this amount R and Ri would have to be increased with a corre- 
sponding increase in initial voltage and greater loss of alternating 
current. 

If this resistance is not sufficient, a low ohmic resistance impe- 
dance coil, X, is placed in multiple with the relay and a cast- 
iron grid for a non-inductive resistance in series with both the 
relay and the track transformer as illustrated in Fig. 238. The 




t 1 



Fig. 238. — Single-rail return. Impedance coil shunting relay. 

impedance coil shown in Fig. 239 offers a high resistance to the 
alternating current, but a low resistance to the propulsion direct 
current. The shunting of the relay and the peculiar construction 
of the track transformer allow a much heavier propulsion current 
to flow without injuring the relay and the track transformer. 
This permits of greater drop of voltage of the propulsion current 
in the continuous rail, allowing longer blocks and heavier cur- 
rents than is possible to use with the other type. 

As a further measure of resistance to the flow of the direct 
current through the track circuit line, an air gap is provided in 
both the impedance coil and the track transformer. The re- 
sistance in the track transformer circuit tends to reduce the flow 
of alternating current when the block is occupied by a train. 
Fuses are provided to protect the equipment should a short 
circuit occur between the block and continuous rails as when tools 
are laid across the track. In double track, the two continuous 
rails can be cross bonded as frequently as seems desirable. 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 221 



The plan indicated in Fig. 238 has the advantage that since 
only a small amount of current flows through the relay and trans- 
former, the wires permit the relay and transformer to be located 
in the tower at interlocking plants without very much additional 
expense. This avoids the necessity of having a secondary relay 
in those cases where the track circuit must be repeated into the 
tower and allows one large transformer to serve all track relays 

and track circuits. Since the resist- 

ance of R and Ri are relatively small, 
their cost is proportionally decreased, 
and their size permits of their being 
mounted in a comparatively small 
space. 

On account of the difference in 
potential between the two ends of 
the block, the single-rail return finds 
its best service in short blocks, as for 
example, the New York Subway, 
where the average length is a Httle 
more than 800 ft. In the operation 
of this Subway, the transmission 
lines carry a 60-cycle current of 500 
volts potential. The current is stepped 
to 50 volts for signal lights and to 10 volts for the track circuit. 
The non-inductive resistance at each end of the block accounts 
for about 2 or 21^ volts so that the current at the single-phase 
relay is practically 5 volts. The grid resistance between the 
transformer and the block rail and between the relay and the 
block rail is 1 ohm. 

The single-rail system is suitable, also, for short blocks through 
interlocking plants where the track layouts are somewhat com- 
plicated. As only one rail is divided, the track circuit instal- 
lation becomes much simpler requiring less expenditure in the 
first cost of construction and less expense for maintenance. 

148. Impedance Coil. — Direct current will have no effect on the 
alternating-current relay except to further magnetize the core. 
Up to a certain point this is not detrimental, and beyond that it 
is taken care of by inserting the impedance coil, Fig. 239, in 
multiple with the relay. The iron core of the impedance ceil is 
made with an air gap so that the extra magnetization does not take 
effect until the direct current reaches a value of 20 amps. 




Fig. 239. — Impedance coil. 



222 



RAILWAY SIGNALING 



149. Track Transformer. — The track transformer, shown in 
Fig. 240, is of the open magnetic circuit type designed for use 
on roads having direct-current propulsion with single-rail return. 
Most of these transformers have secondary coils for supplying 
both track and light circuits. 




PLAN VIEW 

COVER REMOVED 



115^" 




SECTIONAL FRONT VIEW 

Fig. 240. — Transformer. 



SIDE VIEW 

CASE SECTIONED 

Open magnetic circuit type. 



DOUBLE-RAIL RETURN 

150. Direct-current Propulsion.^ — Whenever the propulsion 
current is heavy enough to require both rails to carry the return 
current, the double-rail return system is employed as illustrated in 
Figs. 241 to 243, inclusive. Either direct or alternating current 
may be utilized for propulsion. In order that there may be no 
conflict between the direct current used for propulsion and the 
alternating current used for signaling, impedance bonds either 
with or without iron cores are installed to connect the two rails 

1 Proceedings, Railway Signal Association, Page 130, 1909. 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 223 

at each end of the block. Those with iron cores are shown in 
Figs. 241 and 242, while whose without the core are represented 
by Fig. 243. These bonds have practically no effect on the direct 
current, but offer an impedance to the flow of the alternating 
current. Thus the track is continuous for the propulsion 



rMi 



^A/wv] 



Fig. 241. — Double-rail return system. 



current, but divided into blocks for the signahng current. The 
signaling current may be fed into the end of the block or into 
the center of the block, in which case they are known as ''end-fed'' 
or ''center-fed." Figures 241 and 243 are end fed, while Fig. 242 
is center-fed. 






^ 



n 

Fig. 242. — Double-rail return. Center-fed. 

The iron impedance bond, Fig. 244, is made of six or eight 
turns of large carrying capacity strap copper, wound around a 
laminated core of iron, but insulated from the core. The coils of 
two adjacent blocks are connected by a copper cable tapped into 
the center of each coil as shown in Fig. 241. The coils and core 



224 



RAILWAY SIGNALING 



M 



^M 



icr: 



Fig. 243. — Double-rail return. Ironless impedance bonds. 




SIDE VIEW IN SECTION 

SECTION A-B 

Fig. 244. — Impedance bond. 



AUTOMATIC BLOCK SIGXALIXG ON DOUBLE TRACK 225 

are enclosed in an iron box placed usuall}' between the rails of the 
track. 

As the propulsion current flows into the center of the imped- 
ance bond, and through the two halves of the coil in the 
opposite direction, there should be, theoretically, the same amount 
of return current in each rail with no magnetic effect on the cores 
of the bonds. With the same return current in each rail, there 
should be no difference in potential between the two rails at 
either end of the block and no direct current should flow through 
the relay and track transformer; consequently, there would need 




Fig. 245. — Impedance bonds in place. 



to be no resistance grids nor shunt coil to protect them. In 
practice, however, on account of faulty bonds at rail joints, the 
same amount of return current does not flow through the two 
rails and the two halves of the coil; and this tends to magnetize 
or unbalance the core, reduce the resistance to alternating 
current, and divert more of the signal current from the relay. 
To ehminate this shunting of the relay, the impedance bonds are 
made with an air gap in the core so as to reduce the magnetizing 
effect and the consequent unbalancing. The track transformer 
is not, however, provided with an air gap as it was in the single- 

15 



226 RAILWAY SIGNALING 

rail return type. It is best in designing these bonds to provide 
for an unbalancing of 20 per cent.; that is, to figure that the dif- 
ference in the amount of the current between the two rails may be 
as much as 20 per cent, of the total carried by both. 

The coils used in the Hudson Tubes are 750,000 circular mil 
copper with a resistance of 0.00073 ohm per pair for the direct 
current. They have a continuous-current capacity of approxi- 
mately 1,300 amp. per track and an unbalancing capacity of 
approximately 500 amp. Those used on the New York Central 
are 1,250,000 circular mil copper with a resistance of 0.00014 ohm 
per pair for the direct current. They have a continuous-current 
capacity of approximately 4,000 amp. per track and an unbal- 
ancing capacity of approximately 1,000 amp. The bonds used 
in the Hudson Tubes weigh about 950 lb. and on the New York 
Central about 1,500 lb. per pair when filled -v^ith oil. 

When the alternating current flows through an impedance 
bond, it encounters a much higher resistance than direct current 
does. For example, in the case of the New York Central, 
while the ohmic resistance of the copper to the propulsion current 
is only 0.00028 ohm between the two rails at both ends, the 
resistance to the 25-cycle signal current is 0.06 ohm, or approxi- 
mately 200 times greater, and is explained in the following manner: 

A current through a coil, especially that of an electro-magnet, 
produces a magnetic field that sets up a counter electro-motive 
force in the coil itself. This opposes the voltage and interferes 
with the building up of the current. In the case of alternating 
current, there is no chance to build up a strong magnetic field 
because of such frequent change in direction of the current. The 
greater the number of turns in the coil and the greater the amount 
of iron in the core, the greater is this resistance of impedance. 
The impedance increases also with cycle frequency. A bond 
that would have an impedance of 0.06 ohm at 25 cycles would 
have an impedance of 0.14 ohm at 60 cycles. 

End-fed track circuits may be installed in blocks up to 2,000 
ft. long where 100-lb. rails are used in the track with 0.06 ohm 
impedance bonds connecting them. Beyond this length center-fed 
tracks circuits may be employed with the same rail and bonds in 
blocks up to 6,000 ft., if cross-bonding conditions will permit. 
The center-fed type requires no resistance at the track trans- 
former, while the end-fed frequently does. It does require, 
however, an extra relay with its transformer at each end of the 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 227 

block and a great deal of extra wiring to connect the signals with 
the two sets of relays. This type of bonding and signaling 
finds its best service where traffic is heavy requiring more return 
current than one rail can carry and where the blocks are average 
length or longer. Cross bonding between tracks can be 
done only at the ends of the blocks. On account of the size 
of the housing for the bonds and the size of the cables, the equip- 
ment is not very suitable for terminals and other complicated 
track construction. 

The ironless impedance bonds, shown in Fig. 243, consist 
simply of a much greater number of turns of heavy copper wire 
without the enclosed iron core. The cost of the copper becomes 
such a factor in this case that it is practical to use this system 
only where the current is light enough to permit a smaller wire. 
Resistance is inserted in the track circuit at the transformer, 
and the bonds are connected between the rails as in the previous 
cases. Where the wire connecting the two bonds at -the ends of 
adjacent blocks tap each coil in the middle, full protection is 
afforded against broken rails. In Fig. 243 the bonds are con- 
nected across as usual, but the relay itself is on a secondary 
winding. This prevents the heavy direct current from flowing 
through the relay. On account of there being no iron core, there 
is no unbalancing effect in this system to interfere with the 
impedance. End-fed circuits may be 13-^ miles long and center- 
fed 3 miles long. 

151. Alternating-current Propulsion. — The same type of 
construction is used as for direct-current propulsion, but on 
account of the high voltage of the propulsion current the amper- 
age is low and consequently can be carried by fighter and cheaper 
impedance bonds. The track relaj^s are somewhat different and 
the impedance bonds are made without air gaps. In order that 
the relay may not respond to both currents, the cycle frequency 
of the signal current must be different from that of the propulsion 
current. If the latter should be 25 cycles, the former should be 
60, for these are the values commonly found in practice. 

ALTERNATING-CURRENT SIGNALING ON STEAM ROADS 

152. General. — On account of the difficulties experienced with 
foreign currents interfering with track circuits operated by 
batteries, it has seemed best in many cases to employ alternating 
current for signaling purposes on steam roads. This interference 



228 RAILWAY SIGNALING 

comes in many cases from electric railway lines that run parallel 
to adjacent steam tracks. The signal current may be used also 
to operate signal motors and to give night indications in signals 
and switches. The current for the track circuit for operating 
the signal motor and for lighting switch and signal lamps is all 
taken from the signal mains and stepped down by transformers 
as before. Both rails are divided into blocks, but since there is 
no return propulsion current, no impedance bonds are necessary. 
A continuous track circuit is used the entire length of its blocks, 
thus eliminating the cut section so often necessary with direct- 
current signaling. Blocks as much as 2 miles in length may be 
operated in this manner. 

TRANSFORMERS 

153. General. — The closed magnetic circuit type of trans- 
former, shown in Fig. 246, is designed for use on roads having 
direct- or alternating-current propulsion with double-rail return. 
It is also used on steam roads having alternating-current 
signaling. 

The following suggestions from the 1917 Proceedings of the 
Railway Signal Association are helpful in making connections 
for a series of transformers. 

"Care should be taken to connect all transformer primary leads in the 
same manner, i.e., take one transmission line wire and call it A. Con- 
nect the right-hand lead of all transformers as viewed when looking at 
front of same to this wire. This gives the same instantaneous polarity 
for the corresponding secondary lead of all transformers. This is very 
desirable in order to obtain proper polarity on track circuits and also 
on line circuits when using three-position line relaj^s. 

"In order to insure a uniform polarity scheme, the installation should 
be made as follows: 

"First. — If possible, locate all transformers on the same side of the 
transmission line pole and connect the primary leads to corresponding 
wires. Care should be taken to avoid error due to transposition of the 
transmission line wires. 

"Second. — If necessary to put a transformer on the opposite side of 
the pole, interchange the connections of the primary leads to the line 
wires; this should also be done if the transformer is on the standard 
side of the pole, but a transposition of line wires has been made. 

"Primary leads may be interchanged at the terminal board inside 
the transformer, if they are long enough. This is not considered 
entirely desirable, however, as there is not much space to cross these 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 229 



high-tension leads inside the transformer, hence this is usually done by 
cleating the leads to the underside of the cross arm with porcelain 
cleats and using wire insulated for high voltage for the taps from the 
transformer to the line. 

''Where there is only one secondary winding, it is not absolutely 
necessary to interchange the primary leads as this may be done with the 
secondary leads. It is preferable, however, to interchange the primary 

c 

jzn rh ■ 




PLAN VIEW COVER REMOVED 

l'-4«'!- 




I I 



OIL LINE 




FRONT VIEW 
CASE SECTIONED 

thro' A-B 



SIDE VIEW 

CASE SECTIONED 

THRO' C-D 



Fig. 246. — Transformer. Closed magnetic circuit type. 

leads and have all corresponding secondary leads of the same polarity. 
This insures a uniform scheme in connecting and tagging all wires. 

"In carrying out the polarity scheme, care must also be taken when 
energy is obtained from several sub-stations to insure that corresponding 
line wires from each sub-station have the same polarity. This is ob- 
tained by connecting each primary lead of the signal power transformers 
to the corresponding bus in each substation and taking corresponding 
line wires from corresponding secondary terminals of the power 
transformers." 



230 



RAILWAY SIGNALING 



ALTERNATING-CURRENT RELAYS 

154. General. — Alternating-current relays may be the single- 
phase induction type energized by the track circuit only; or they 
may be two-winding, either the induction motor type or the poly- 
phase type, one winding of which is energized by the transmission 
line and the other by the track circuit. The single winding is 
simpler in construction, but requires more energy to actuate it 
than the two-winding. It would require a high voltage to send 
a current through a block 2 miles long and operate a single-phase 
relay successfully, so high that most of it would be lost by leakage. 
In the case of the two-winding relay, however, the transmission 
winding, which is located practically at the relay, is usually 55 to 
110 volts and furnishes most of the energy with a very slight loss. 
The track winding of this relay requires very little energy. 
Therefore, the single-phase is better suited for short blocks and 
the two-phase for long ones. Since most of the energy is fur- 
nished by the local winding, it is possible to use long track circuits 
as compared with direct current. If all the energy had to be fur- 
nished through the track winding, the block could be practically 
no longer than with direct current. 

Union Switch and Signal Company Designs 

155. Vane Type.^ — The two pole pieces in the vane type of 
alternating-current relay are made up of laminated iron cores 

instead of solid iron cores as is the 
case with the neutral relay. Be- 
tween the two cores wound with 
wires swings an aluminum vane 
mounted on a horizontal shaft. 
The vane is constructed to swing 
through an angle of 90 degrees. 
The alternating current flowing 
through the windings induces an 
alternating flux in the iron core 
and in the gap between the pole 
faces of the core. A copper 
ferrule, Fig. 247, encircling the 
upper half of each pole face, acts 
just as a short-circuited secondary on a transformer to produce 
a counter magneto-motive force opposing that of the primary 
^ Proceedings, Railway Signal Association, 1910. 



i 



FERRULES 



VANE CURRENT 




Fig. 



-Operating element 
vane relay. 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 231 

winding. This counter magneto-motive force causes a lag in 
the passage of the magnetic flux through the portion of the 
pole face encircled by the ferrule, with the result that the maxi- 
mum and zero values of the magnetic flux in the part of the pole 
face encircled by the ferrule occur a short interval of time after 
the corresponding values are reached in the other half. There is 
then a traveling of the magnetic field over the pole face towards 
the portion that is enclosed in the ferrule. These lines of force 
traveling in this direction carry the vane along with them causing 
it to rotate about its axis. 

Model 15 vane type, shown in Fig. 248 can be operated either 
as a two-position or a three-position relay. The two-position 




Fig. 248. — Model 15 vane type relay. 



relay may have either one or two windings. The various arrange- 
ments are known as single-element two-position, two-element two- 
position and two-element three-position. The single element 
is used either on single-rail return or on center-fed double-rail 
return systems. 

156. Ironless Galvanometer Type. — This type can be used 
either in track or line circuits, but it offers its chief advantage 
when used as a track relay. The field or stationary winding, 
which is the two outside coils, is connected to the transmission 
line; while the armature, which is the movable element, is con- 
nected to the track circuit. Most of the energy can be supplied 
by the transmission line leaving a very small portion to be fur- 
nished by the rails. This allows track circuits to be a mile or 
more in length without excessive loss by leakage. Current of 



232 



RAILWAY SIGNALING 



similar characteristics must flow through both windings at the 
same time to make the relay operate. Direct current from the 
rails has no effect either to operate or to hold the armature since 
it can act only on the one winding, which contains no iron. 




SECTIONAL END VIEW 

Fig. 249. — Three-position ironless galvanometer relay. 



FRONT VIEW 
GLASS SECTIONED 



157. Iron Core Galvanometer Type. — The relay shown in Fig. 
250 is a two-phase wire wound type whose operation depends 
upon the phase relations of the current in the track and trans- 
former windings. It is built in the form of a motor in which the 




SECTIONAL BACK VIEW SECTIONAL SIDE VIEW 

Fig. 250. — Iron core galvanometer relay. 

armature makes only a part of a revolution, and the field and 
armature are connected in multiple or are excited from separate 
sources. Its characteristics are very similar to the Ironless type, 
and it is generally interchangeable with it for steam-road service. 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 233 

It is not recommended for electric-road practice. It is slightly 
more economical of current than the Ironless type. 

158. Centrifugal Frequency Relay. ^ — The frequency relay is 
designed for use in the track circuits of a railroad having alter- 
nating current for both propulsion and signaling. The number 
of revolutions per second, n, at which an induction motor oper- 

ates is calculated from the formula, n = p^ where / is the cycle 

frequency of the stator winding, and P is the number of stator 
poles. If a current should have 60 cycles per second and a 






Fig. 251. — Centrifugal frequency relay. 

stator 12 poles, the motor would make 10 revolutions per second; 
while if the current should have 25 cycles per second and the 
same number of poles, the rotor would make a little over 4 
revolutions per second. 

The stator windings of the Union frequency relay is made 
up of two elements so that the instrument may operate either as 
a single-element or two-element relay. The proper phase relation 
of the current flowing through the two windings is adjusted by 
inserting suitable resistances in the circuits. The centrifugal 
apparatus is constructed somewhat after the manner of the 
governor on a steam engine. With 60-cycle current the rotor 
turns with sufficient speed to cause the balls to swing out far 

^ Signal Engineer, February, 1914. 



234 



RAILWAY SIGNALING 



enough to lift the operating collar the proper amount for closing 
the contacts. With 25-cycle current the rotor does not acquire 
sufficient speed to lift the centrifugal apparatus to make the 
necessary contacts for operating the signals. 

159. Radial Contact Polyphase Induction Type. — This instru- 
ment, shown in Fig. 252, is built on the induction motor plan 
and can be used either as a track or line relay. As the shaft 
rotates it causes the fingers to engage with contacts located 
around the periphery of the case. The chief advantage of this 
type of relay is its capacity for a large number of contacts. 




Fig. 252. — Radial polyphase relay. 
GENERAL RAILWAY SIGNAL COMPANY DESIGNS 

160. Universal Alternating Current Relay.— The universal 
alternating current relay is an induction type, with the stator 
winding made up of eight form-wound coils and with the rotor 
shaft mounted vertically. The contact movement is operated 
by contact rolls, as shown in the illustration, Fig. 253. The 
relay is made either direct connected or pinion and sector con- 
nected. The direct connected is recommended for average track 
circuit conditions, while the pinion and sector connected is 
recommended for long track circuits having unfavorable ballast 
conditions and for special work. The relay may be fitted for 
either single-rail or double-rail track circuits, and may also be 
equipped for fine circuits. It may be converted to a three- 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 235 

position relay by adding counterweights and readjusting the 
contacts. 




Fig. 253. — Universal A. C. relay. 



161. Models 2A and 2B Two- and Three -position Relays. — 

The Model 2A relay shown in Fig. 254 is designed primarily for 
use as a track relay on steam roads, or electric traction lines 
employing direct current for propulsion. It may, however, be 
used as a line relay. The construction of this relay is very much 
like the two-phase induction motor type except that it has a rotor 
made of aluminum, a non-magnetic metal, instead of iron. One 
phase of the winding is energized by a transformer located near 
the relay and the other by the track circuit. 

These instruments are made to operate either as two-position 
or three-position relays. The two-position may have either the 
direct-connected arrangement, as illustrated in C, or the sector 
and pinion arrangement, as shown in D. As the direct-connected 
relay is arranged with a crank and lever directly connected to the 
rotor for operating the contact fingers, it has a quicker pick-up 
and drop-away, but requires more energy for operation. 
The three-position relay always has the pinion and sector 
arrangement. 

The Model 2B is designed primarily for use as a line relay, 
although it is employed as a track relay on steam roads having 
short track circuits. The two-position relay is used, also, as a 
track relay where there are short track circuits on electric lines 
employing direct current for propulsion. The sector operates a 
lever that lifts the fingers to make contact. 



236 



RAILWAY SIGNALING 



The Model 2B Time-element relay, has a gear train in place of 
the pinion and sector movement for operating the contacts. 
Time-element relays are of two kinds: (1) Time-element closing, 




VIEW SHOWING CR&NK AND LEVER ARRANGEMENT 
FOR TWO POSITION DIRECT-CONNECTED REUYS 



VIEW SHOWING SECTOR AND PINION ARRANGEHENT 
FOR THREE POSITION RELAYS 



Model 2A relay. 




Model 2B relay. 
Fig. 254, part 1. Models 2 A and 2B relays. 

in which the front contacts are not made until a predetermined 
time after the relay is energized and are immediately broken 
when the relay is deenergized. They operated as single-circuit 
relays only. (2) Time-element opening, in which the front 
contacts are made immediately when the relay is energized and 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 237 



are not broken until a predetermined time after the relay is 
deenergized. They operate as two-circuit relays only. 





Fl-G. 



Model 2B, time element relay. 
254, part 2. Models 2A and 2B relays. 



162. Model 2A Two-position Centrifugal Frequency Relay. — 

The frequency relay, illustrated by Fig. 255, is designed prin- 
cipally for service as a track relay for double-rail return circuits 
where alternating current is used for propulsion. It is employed 
on steam roads only at crossings with electric lines having alter- 




FiG. 255. — A. C. relay. Model 2 A, two-position centrifugal frequency type. 

Rotor operated. 

nating current for propulsion. It may be used, also, on short 
single-rail return circuits or as a line relay. 

When the track section is not occupied by a train, the rotor 
operates at a speed proportional to the frequency of the signaling 
current, which is usually 60 cycles a second. When the rotor 
turns at this speed it rotates the centrifuge apparatus at such a 
rate as to cause it to assume a position more nearly at right 
angles to the axis of rotation. This causes a thrust on the lever 
arm, which lifts the fingers to make the proper contacts for 
closing the signal circuits. If a train occupies the section and 
short-circuits the signaling current, and the rotor runs at a 



238 



RAILWAY SIGNALING 



slower speed corresponding to that of the propulsion or stray 
current frequency, the centrifuge apparatus will not assume 
the proper position to cause the finger contact. This construc- 
tion prevents the propulsion current from operating the relay. 
As the relay operates only in one direction, it gives broken joint 
protection when adjacent track feeds have staggered polarities. 

ALTERNATING-CURRENT TRACK AND SIGNAL CIRCUITS 
163. Two-position Signals. — Figure 256 represents the track 
and signal circuits installed on a portion of the Subway in New 
York. This is a single-rail return system with direct-current 
propulsion, as was previously explained. The vane type of relay 
was used in this installation. 




BATTERY 



Fig. 256. — Track and signal circuits on a portion of the New York subway. 
(Union Switch and Signal Co.) 

Figure 257 illustrates the track and signal circuits used on a 
portion of the Long Island Railroad.^ This is a center-fed con- 
struction with the vane type of relay used at each end of the block. 

Figure 258 represents the signaling plan used on another 
portion of the Long Island Railroad. The track transformer is 
attached to the rails near the middle of the track section, and a 
galvanometer type of relay is used at each end, the one at the 
exit end of the track circuit being a two-position and the one at 
the entrance end a three-position relay. The armatures of the 
relays are energized directly from the track circuit. The field 
of the relay at the exit end of the track circuit is energized 
directly from the 55- volt transformer; the field of the relay at 

1 Pages 412 and 413, Proceedings Railway Signal Association, 1910. 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 239 




\ 



1 

D 



SiS 



(H 



KM 



s 



l^ 



Eh 



I 



O (H 



240 



RAILWAY SIGNALING 



the entrance end of the track circuit is energized over the Hne 
wire extending up to the exit end of the track circuit and over the 
point of the relay at this end, thence through the pole-changer to 
the 55-volt transformer. 

The West Jersey and Seashore Railroad signal installation, 
represented by Fig. 259, has center-fed track circuits with 
blocks averaging about 4,000 ft. in length. ^ There is a wire wound 
armature type of relay at one end of the block and a step- 
up transformer at the other. The step-up transformer is con- 
nected to the relay by line wire furnishing the current for the 
armature winding. 

Figure 260 represents a signal installation on a portion of the 
N.Y.N.H. & H.R.R.^ The signal and lighting current is 110 
volts, 60-cycle frequency, stepped down from a 2,200-volt trans- 



¥ 



.-_Ju^^ 



.-rP200Volt-25'^A.C Mams 



5ignalancl 
bgthing- 

Inducfive bonds ^^^^^^^^^^ 
not .shown ■■;-• 



n? 




HTfuses 

Track Transformer 



^ 



Pole changer on \\ 
Home&lade fp-.-Jj 



a 



^CVaneTgpe ;; 

Slow acting ni i ■; 



/?. C Ga/vanomefer 
Type Track Re/ac/ 



Q ^ 



Fig. 258. — Semi-wireless control, L. I. R. R. (Union Switch and Signal Co.) 

mission line fed from a 11, 000- volt power transmission line. 
The track circuit equipment was designed for either 550-volt 
direct-current or 11, 000- volt, 25-cycle, single-phase alternating 
current. As it was necessary to cross-bond the track every 
3,000 ft., cut sections were employed in each block. Current is 
supplied to the track circuit by a transformer located at the middle 
of the section. Frequency relays designed to operate at 60 
cycles, installed at each end of each section, control the signal 
circuits. There is also an impedance bond at each end of each 
track section. 

164. Three -position Signals. — Figure 261 illustrates the Union 
typical track and signal circuit plan for three-position signaling 
arranged for direct-current propulsion with double-rail return. 

1 Proceedings, Railway Signal Association, 1910, 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 241 




16 



242 



RAILWAY SIGNALING 




AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 243 




244 



RAILWAY SIGNALING 



Figure 262 is a diagram of track and signal circuits installed 

by the General Railway 
Signal Company on a por- 
tion of the Cumberland 
Valley Railroad, a double- 
track steam line. The sig- 
nal transmission line carries 
a current of 4,400 volts. 
Transformers step the cur- 
rent down to 110 volts for 
the signal circuits and to 
2, 4, 6, 8, and 10 for track 
circuits. This range in 
voltage is obtained by plac- 
ing an adjustable resistance 
in series with the trans- 
former leads. All the auto- 
matic track circuits are 
arranged for wireless con- 
trol by operating three- 
position track relays. The 
90-degree, or distant indi- 
cation, is given by reversing 
the polarity of the track 
circuit by means of the 
pole changer on the signal 
mechanism. 

The track circuits vary 
in length from 2,000 to 
8,000 ft. 4 volts are re- 
quired to operate the track 
circuits up to 5,000 ft. and 
6 and 8 up to 8,000 ft. 
The relay is the polyphase 
three-position type, the 
local phase being wound 
for 110 volts. The relay 
operates in one direction to 
bring the signal to the 45- 
degree position and in the reverse direction to the 90-degree 
position. It stands in the neutral position when shunted. 




AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 245 

Figure 263 is a diagram of typical circuits used by the same 
company in installing the signal system on a portion of the double- 
track line of the Southern Railway. The current furnished by 
the signal transmission line has a potential of 4,400 volts. Trans- 
formers step the current down for the 110- volt induction motors 
used to operate the signal mechanisms and for the 110- volt 
primary winding of the separate track transformers. The 
secondary taps of the track transformers, arranged to secure 
any voltage from 1 to 10 in steps of 1 volt, furnish current to 

SSV.-//0V(yrZ2(?V.AC. 
From Line Transformer 



1 2 V. Lamp s 
0) W )--, 



Pnmotrtj 
Local 




Track 



1 •— tL To 9 Von Track* 
' s ^ V/inaina[ 



-:i-U:- 



::r*-tr: 



Fig. 263. — Typical circuits used on the Southern Railway. 



energize the three-position track relays. The track circuits are 
end-fed and are continuous from one signal to the other, varying 
in length from 300 to 14,000 ft. The 45- to 90-degree movement 
of the signal is secured by a reversal of the track transformer 
leads. In the figure, when a 12-volt local is used, the winding 
on No. 2 track transformer is omitted and the connection is made 
as indicated by the dotted lines. P is the pole-changer on the 
signal, Q is the track transformer, usually the K-\ type, i^ is a 
choke-coil air-gap arrester, *S is a resistor in the ground lead for 
circuits, T is an air-gap arrester without choke-coil, C/ is a low- 
voltage ground element, F is a low-tension ground wire, W is the 



246 



RAILWAY SIGNALING 



Tgif^ 



iji It 



^.. 



m 

[m4 



^ g 



ilnil 



^ 



k 



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I^lJ 



— ^1 

9^^ 



g ^ 



m 



k' 






fi* 



^ 



signal pole or case, X is an adjust- 
able track resistor, and F is a 
three-position polyphase track 
relay. 

Figure 264 shows a typical cir- 
cuit plan for signals installed on 
the Unes of the New York 
Municipal Railway Corporation. 
It provides for one full block 
overlap with automatic train 
stops used in connection with the 
signals. (A) in Fig. 265, shows the 
control limits for the circuits, 
while (B) shows the indications 
of signals and the positions of 
automatic stops with a train in a 
block. The reason for retaining 
the stop on the first track section 
in advance of the signal is that 
occasions frequently arise where it 
becomes necessary to operate 
trains against the normal direc- 
tion of traffic, and this scheme 
provides a very simple means of 
automatically clearing the stop for 
such moves. 

Normal danger signals having 
time-element control are used on 
down grade track or on approaches 
to sharp curves where it becomes 
necessary to limit the speed of 
trains regardless of whether or 
not the track is occupied. The 
control is secured by the use of 
time-element relays in conjunction 
with approach sections that are 
generally two blocks long. The 
control limits for this scheme are' 
the same as in (A) with the normal 
danger time-element feature added. 

In (C) a train approaches sig- 
nal 5 with the track ahead un- 



AUTOMATIC BLOCK SIGNALING ON DOUBLE TRACK 247 



occupied. If the train occupies the track between signals 9 and 
7 for the required time, for example 14 seconds, signal 5 will 
display a yellow or caution indication that will cause signal 7 to 
change from a yellow to a green indication, as shown in (D). 
As the train proceeds and occupies the track between signals 7 
and 5 for the required length of time, signal 3 changes from a red 
to a yellow indication and this, in turn, causes signal 5 to change 
from a yellow to a green indication. If the train should pass over 



+= 

tnrz: 



4^ 

^ Oreen 



^ 



^tO 



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(A) 



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(B) 



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-\^ — ^ \^ 



^ Red ^ Green 



4 



^^- 



4^ 



S^/Fed ' 7 '^Yellow ' S ^Red '3 ^/?ed ' I ^Red 

(Cj 

-^4 E^iQ> h^ ^^ f^ r- 



9^ Red 



T^Green ' 5 "^Yellow '3 "^Red 
(D) 



/ ^Red 



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I Q:^ 1 0^^ le^ l O^^ 1 0^ \ 0^ i\WiWiSWi'i< > 

^jj9-^ Jzfi. „ y# ^j# "r jw f^ _ 



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'Red' 



Red (E) Red Red Red 



Tram 5 
MSB I Q>. 



Tram 2 



Sfirtion 



^ — v=% — i^i^ [^ — ^ 



Yellow 



Red 



Red f^ea 



Yellow 

Fig. 265. — Control limits and indications on lines of the New York 
Municipal Railway Corporation. 

the track between signals 9 and 7 in too short a time to permit 
signal 5 to change from red to yellow, signal 7 would be passed 
indicating yellow or caution, and the train would be forced to 
occupy the track betv/een 7 and 5 just about twice as long as 
would have been the case if it should have waited and allowed 
signal 7 to indicate green before passing it. If the train should 
continue at a speed faster than should be permitted and should 
pass over the track between 7 and 5 before the time-element relay 
should have operated, the train would be automatically tripped 
at signal 5. The time-element control, as used on the Manhattan 



248 RAILWAY SIGNALING 

and Williamsburg bridges, limits the train speed on the down 
grade portion to about 15 miles an hour. 

In approaching stations the time-element is involved with 
extended length of control. In this case the blocks are short and 
the control is extended to cover three or more track circuits, 
depending upon conditions. The signals are normally clear and 
operate as shown in (E) and (F) . The long-dashed lines indicate 
the regular two-block overlap control and the solid lines indicate 
the extended control, which is cut off by means of the time- 
element relays if the speed of a following train is reduced as 
predetermined by the timing of the time-element relays. (E) 
shows signal indications with a train occupying the track at a 
station, while (F) shows how a train may follow provided its speed 
is reduced. 

With train No. 1 at the station, signals 1, 3, 5, 7, and 9 indicate 
red, and signal 11 yellow. As train No. 2 approaches signal 11 
at a predetermined reduced speed, signal 9 changes from red to 
yellow allowing signal 11 to change from yellow to green. As 
train No. 2 occupies the track between signals 11 and 9, signal 7 
changes from, red to yellow and signal 9 changes from yellow to 
green. Thus each signal, 11, 9, and 7, changes to display a green 
indication and signal 5 changes to display a yellow indication 
provided train No. 2 approaches each at a predetermined reduced 
speed. With train No. 1 still in the station, train No. 2 has to 
stop at signal 3. The time-element feature works in practically 
the same manner as in the normal danger scheme, except that it is 
used to reduce the length of control. That is, if train No. 2 
exceeds the predetermined speed the extended control is not cut 
off, the signals do not change from the red indication and the train 
is automatically stopped. 



CHAPTER XIV 
AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 

165. General. — Automatic block signals provide for efficiency 
and safety in operation on a single-track road as well as on a 
double-track line. When a single-track line reaches the point of 
congestion, the installation of automatic block signals will relieve 
the congestion and prolong the day when double-tracking 
becomes necessary. The installation of the signals requires very 
little time, expense and labor in comparison with the construction 
of a double track. Some roads report that the capacity of a 
single track has been increased by 20 per cent, with the installation 
of automatic block signals. 

166. Union General and Special Plans — TDB System. — In 
double-track block signaling, the signals must protect trains 




Fig. 266. — Union plan of single track signaling. 

that follow each other; whereas in single-track operation the 
signals must protect not only trains that run in the same direc- 
tion, but also those that run in the opposing direction. In 
order to do this several plans have been devised, one of which is 
the two-position scheme by the Union Switch and Signal Com- 
pany. Figure 266, shows the relative location of home and 
distant signals in the case where the stations lie about 4 miles 
apart. Should the distance be greater, one or more sets of 
intermediate home signals should be added in order that the 
blocks should not be so long as to cause delay to traffic. 

The lines above and below the signals in Fig. 266 represent 
the length of track that controls the signals and holds them in the 
stop position; for example, the line from signal 1 extends to the 
right as far as the end of the first track section beyond signal 4, 

249 



250 ■ RAILWAY SIGNALING 

and if a train should occupy any portion of the track between 
these two points signal 1 would be in the stop position. Like- 
wise, the control for signal 4 extends to signal 1 so that if a train 
should be at any point between signals 1 and 4, signal 4 would be 
in the stop position. A train leaving station A and moving to 
the right will place 4 to the stop position as soon as it passes 
signal 1, and a train moving to the left will place signal 1 in the 
stop position as soon as it enters the section to the right of 
signal 4. This overlap of one track section affords head-on 
protection and eliminates the possibility of trains passing signals 
4 and 1 both in the clear positions at the same time. 

The reason for placing signals 3 and 4 one track section apart 
is for head-on protection also. Should opposing trains pass 
signals 1 and 6 at the same time, they would stop at signals 3 
and 4 with a full track section between them. 

There is a home signal at the beginning and end of each siding. 
The distant signals are governed by the siding entrance signals. 
The control for home signal 5 extends to distant signal 8 and the 
control for home signal 8 extends to distant signal 5. As soon 
as a train moving to the left passes distant signal 8, the home and 
distant signals 5 will go to the stop and caution positions. As 
soon as it passes home signal 8, signal 10 will assume the proceed 
position. This arrangement allows a train occupying the main 
track within the station limits to be fully protected from trains 
approaching on either side; at the same time, since signals 3 
and 10 both give proceed indications under these conditions, a 
train can reach the siding without passing any home signal set 
at the stop position except the siding entrance signal near the 
switch. 

Sometimes where the distance between stations is short, home 
signals are placed only at stations, as shown in (A), Fig. 267. 
Sometimes where the distance is the ordinary length they are 
placed at the stations only for protecting trains within station 
limits. The control between stations is as shown in (A), Fig. 267, 
and that through stations as shown in (B). A preliminary over- 
lap section, as shown at Station A, Fig. 267, is generally made in 
favor of superior trains so that two trains will not pass at the 
same time home signals set at the proceed position. 

Figure 268 is a wiring plan for the signals in Fig. 266. Figure 
269 is a wiring plan where intermediate signals come opposite 
distant signals, which frequently occurs in continuous blocking 



AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 251 



^ 



4 



4 



7^ 



} 



1 






"^1 



gl 



2 .^ 

I; CO 

I -^ 

*2 '-^ -S 

>5 oq bD 

Co <> c 



252 



RAILWAY SIGNALING 




where stations are not over 
23-^ or 3 miles apart. Fig- 
ure 270 shows the location 
of home signals at the end of 
the siding with some details 
of trunking arrangements. 

Figure 271 represents a 
different Union plan of two- 
position signahng. This sys- 
tem was installed on 13.2 
miles of single track on the 
Washington, Baltimore and 
Annapolis Electric R. R., a 
freight and passenger inter- 
urban Hne having 1,200-volt 
direct-current power for pro- 
pulsion purposes. There are 
eight standard blocks and 
one special, employing 17 
semaphore signals and 16 
hght signals. The longest 
block is 11,610 ft. and the 
shortest is 5,430 ft. with an 
average of 8,680 ft. There 
are four signals for each 
block, which extends from 
one siding to another. Two 
of the signals are the sema- 
phore type, located at each 
end of the block; the other 
two are the color-light type, 
each about 1,000 ft. in ad- 
vance of a semaphore signal. 

The double-rail return sys- 
tem is employed with track 
sections extending the full 
length of the block. One 
track relay is located at 
each end of the track cir- 
cuit and is energized by a 



AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 253 



transformer feeding at the middle of the block. The relay at 
the west end of the block is controlled by the track to a point 
about 1,000 ft. east of the center of the block, while the relay at 
the east end is controlled by the track to a point the same dis- 
tance to the west of the center. Each semaphore signal is 
controlled by both track relays, while each light signal is con- 




FiG. 269. — Wiring plan where intermediate signals come opposite distant signals. 

trolled by the relay at the opposite end of the block. An east- 
bound car entering the block with signal 115 at clear, places 
this signal as well as 102 and 104 in the stop position. As the 
car passes 113 at clear and reaches the western control limit of 
this signal, it sets 113 in the stop position. As soon as the car 
passes 102, all signals in the block assume the proceed position. 




Fig. 270. — Arrangement for the location of a home signal at the end of a siding. 

The light signals would act as a check should two approach- 
ing trains pass opposing semaphores at the same time; for example, 
if an east-bound car should pass signal 115 at the same time that a 
west-bound car should pass 102, the east-bound car would be 
stopped by signal 104 and the west-bound by signal 113. 



254 



RAILWAY SIGNALING 




AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 255 



From the 2,200-volt signal transmission line current is stepped 
down to 110- volt for signal circuits and to 10- volt for track cir- 
cuits. Each light signal is controlled by a 110-volt line relay, 
which is in turn controlled by the galvanometer type of track 
relay. The lamps behind the green lens are controlled by the 
front contact of the line relay, while those behind the red lens are 
controlled by the back contact of the same relay. The semaphore 
signals are controlled by contacts on the track relays and also 
by contacts on the light signal line relay, without the use of extra 




Fig. 272. 



•Upper left-hand quadrant semaphore signals on the Washington, 
Baltimore and Annapolis Electric R. R. 



line relays. The semaphore arm operates in the upper left-hand 
quadrant as illustrated by Fig. 272. 

The "T D B" (Traffic Direction Block) system is another 
scheme devised for single-track signaling used largely in interurban 
service.^ The length of block for opposing movements is the 
distance from one siding to the next, while the length for follow- 
ing movements is just half the distance between sidings; that is, 
there are two ''following" blocks in each ''opposing" block. 
There are four signals in each "opposing" block, two near the 
ends of the sidings and two near the middle of the block. The 

1 Pages 351-363, A. C. Signaling, U. S. & S. Co. 



256 RAILWAY SIGNALING 

control limits for the different signals are shown by Fig. 273. 
Each signal at a siding governs both ''opposing" signals in the 
block, while the intermediate governs only the one. All signals 
govern to the first signal in the rear for following movements. 
The circuits of the entire system are operated by alternat- 
ing current. The signal transmission line carries a potential of 
2,200 volts and from this the current is stepped down by trans- 
formers to 110 volts for signal circuits and to 10 volts for track 
circuits. The double-rail return system is employed for the 
propulsion current. 



LINES LEADING FROM SIGNALS INDICATE SECTIONS OF TRACK GOVERNED AS FOLLOW 

^- = FDR EAST BOUND CARS ONLY -- FOR WEST BOUND CARS ONLY = FOR EAST i WEST BOUND CARS 

NOTE- An east bound car between sidings blocks all west bound cars from same territory, and vice versa 
A car on a siding does not allecl llie signals 

Fig. 273. — Signal control limits. 

Figure 274 shows the indications given by each signal as one 
or more cars proceed through the blocks. In case A, there is 
a west-bound car approaching the siding x, and the opposing 
signal 2 is in the stop position. In B, the car is passing signal 1, 
setting it in the stop position, and also setting signals 4 and 6 in 
the stop position. Signal 2 goes to clear as soon as the train 
passes out of its block. In D, the first car, R, has proceeded to 
signal 3, and a following car has approached signal 1. Signal 1 
protects car R from a following car, while signals 4 and 6 protect 
it against an approaching car. As car R has passed signal 4 
in E, signal 1 has cleared for car >S. InF, car S has entered the first 
"following" block, while car R is in the second "following" 
block. Signals 1 and 3 protect against following movements and 
signals 4 and 6 against opposing movements. In G, car R has 
entered the next "opposing" block while car >S is following and 
both are protected by signals in the front and rear. The operation 
for east-bound cars is similar. 

H, I, J, K and L, show the positions of cars and the indica- 
tions of signals as the cars meet at siding Y. Cars between 
X and Y do not in any way affect the signals between Y and Z as 
M, N, 0, P, and Q indicate. 

Each opposing block has one track circuit with a relay at 
each end operated by current from a transformer located at the 



AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 257 

middle of the block. In the block X-Y, Fig. 275, there will be 
one track relay at signal 1 and another at signal 6. Normally, 
signals 1 and 6 are controlled by both track relays, or the entire 
section of track between signals 1 and 6. Signal 3 is controlled 
by the track relay at signal 6, and signal 4 is controlled by the 
track relay at signal 1. 



X— ^' 



^=^ 



^ 



^n^ 



0.^' 



.^7=^ 



^^^^ 



^^^7=^ 



^ — ■ 



«^^ 



■'J^ 



^7^ 



«TI7^ 



S^' 



^n?^ 



f-^' 



Fig. 274. — The TDB system; effect of train movements on signal indications. 

A west-bound car entering the block X-Y at X, will deenergize 
the track relay at signal 1, thereby setting signals 1, 4 and 6 
to the stop position. As signal 3 is controlled by the track 
relay at signal 6, it will not be set at stop until the car reaches 
the point where it affects this track relay. 

The car in deenergizing relays Tl and 4L, energizes stick 
relay 3aS which is used to clear signal 1 after a car has passed 
signal 4. This stick relay cuts out the control of signal 1 from 

17 



258 



RAILWAY SIGNALING 



the track relay ^6 and the Une relay 3L. As the car proceeds, 
passing signal 3, the track relay 7^6 is deenergized, setting signal 
3 at stop and still holding the other three signals at stop. When 
the car passes signal 4, track relay Tl is again energized and 
signal 1 is cleared. Incidentally, signal 4 is cleared because the 
track relay at signal 1 is energized, but this has no effect on west- 
bound movements. When the car has passed signal 6 all signals 
and relays again assume their normal positions unless a second 
car has entered the block at signal 1 before the first car passed 
signal 6. The operation for east-bound cars is similar. 




Fig. 275. — Circuit scheme for TDB system. 

The stick relay 3*S is active only in connection with west- 
bound movements; east-bound movements have no effect upon 
it. Therefore, an east-bound car will set signal 1 at stop when 
signal 6 is passed. Another stick relay 48, is used to limit the 
control of signal 6 in a similar manner for east-bound movements. 

The circuits are so arranged that but one of the two line 
relays can be energized at any one time. It will be evident that 
if west-bound car should pass signal 1 at the same time that an 
east-bound car should pass signal 6, signals 3 and 4 being directly 
controlled by the track relays, would afford positive protection. 

Figure 276 represents a single-block "T B D" installation with 
four color-light signals on the Cleveland, Southwestern and 
Columbus Railway at Puritas Junction, Ohio.^ This line is 
electrically operated, handling both interurban passenger and 

1 Volume XIV, 1917, Proceedings, Railway Signal Association. 



AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 259 

freight service. It is a double-rail return system having 600- 
volt direct current to supply the trolley for propulsion, and 
2,200-volt, 25-cycle, single-phase alternating current to operate 
the signal system. There are two types of transformers; one, an 
adjustable filler type, T3, that steps the current from 2,200 to 
110 volts for the line circuit and from 2,200 to 10 for the center-fed 
track circuit; the other, a constant-potential type, T2, that steps 
the primary voltage from 2,200 to 110 for the line circuit at each 
end of the track. The track relays are the two-position galva- 
nometer type with 110- volt local coils, while the hne relays are 
110-volt, two-position vane type. The signals are the Union 



A.C.Linesr-, 



r^Jt^bu Purchaser ^gWmrf 

J -~ -"- '-'-^ l emn+A] .... 



6 loot- \- 







mB-Wac/ Re/at/ Box 
T] Lightning Arresf-er Box 
^M'^nsfarrf Pafprifial Trans. 

W Pr}watyZ200V. SeciiOV.2S~ 
rjwj Adjuifable Filler Trans. Z200V. 



Fig. 276. — Wiring plan for light signals on the C. S. & C. Ry. at Puritas Jet., O. 
{Proceedings, R. S. A., 1917.) 



Model 13, light type, designed to give both day and night indi- 
cations by lights only. 

167. General Railway Signal, General and Special Plans, A. 
P. Block System. — (A), Fig. 277, represents a general arrangement 
of three-position signals for single track. The full lines above 
and below the signals mark the length of control for the stop 
position as before, but the dotted lines shown in addition indi- 
cate the control for the caution position. If a train should be at 
any point between signals 1 and 5, 1 would be in the stop position. 
If it should be at any point between signals 3 and 7, 3 would be in 
the stop position and 1 in the 45-degree or caution position. In 



260 RAILWAY SIGNALING 

(B) a train at any point between signals 3 and 7 would place 3 
in the stop position and 1 in the caution position. In (A) signals 
3 and 4 indicate in only two positions, stop and proceed. If 
a train should occupy the track between signals 3 and 7, signal 3 
should show a stop position; but if not, signal 3 should give a 
proceed indication. Signal 5 should show caution if there is a 
train between signals 7 and 10. 

Another plan for three-position signaling on single track 
has been devised, known as the Absolute Permissive System — 
absolute for opposing trains and permissive for following trains. 
When a train enters a block, it sets all the opposing signals in 



x--k , — \ 



10 



I ^ 3 , S , 7 , 9 , M , 13 

^:^ ^^^^ ' x'^.- N^ -"i \ ^ 



X 



B 
DIAGRAM NS I One pair of Signals BCTvyccN Sidings 

(A) 



D^ 



■%— \- 



F ' 6 °^ ' 10 '^ ' 12*^^ ' 14*^ 



3 , 5 , 7 



A ^ B ^ 

DIAGRAM N? 2 TWO PAIRS OF SIGNALS BETWEEN SIDINGS 

(B) 
Fig. 277. — Three-position signals for single-track. 

that block to stop, but controls only two signals in the rear 
just as in double-track operation. Figure 279 shows the spacing 
of the signals and the lengths of their controls. There is one 
permissive and one absolute signal at each end of each siding and 
there are four intermediate permissive signals between sidings. 
An east-bound train leaving siding A, Fig. 279, sets 2, 4, 
and -6 all to stop and 8 and 10 to caution; likewise a west- 
bound train leaving siding C sets 9, 11, and 13 to stop and 5 
and 7 to caution. After the east-bound train passes 2, 2 will 
go to clear; after it passes 3, 1 will go to caution; and after it 
passes 5, 1 will go to clear and 3 to caution. Diagrams Nos. 4, 
5, 6, 7, Fig. 280, show the positions the signals take as a west- 
bound train moves from B to A. Diagrams 8, 9 and 10 show the 
positions that signals take governed by two trains moving with 



AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 261 



equal speed in opposite directions from A and C. Diagram 11 
shows the positions of signals when 
one train has reached the siding B 
in advance of the other train. 

In order that a train may con- 
trol all the signals ahead of it 
between sidings for opposing move- 
ments, but only the first two signals in 
the rear of it for following move- 
ments, a stick relay is used with 
wiring as shown in (A), Fig. 281. In 
this figure, H is the control relay for 
the signal in block A, T is the track 
relay, and S is the stick relay. The 
circuit breaker operated by the signal 
is closed when the arms stand any- 
where between 45 and 90 degrees. 
The current that energizes relay S 
flows through the signal circuit 
breaker and the back contact of track 
relay in block A. The holding cir- 
cuit of S is through the back con- 
tact of ZZ" and the front contact of S 
itself. 

A train entering A from left to 
right will deenergize relay T of that 
block causing its armature to drop 
and to deenergize H until the signal 
blade has dropped below the 45- 
degree position. This is sufficient 
time to energize S and cause its 
armature to make front contact, com- 
pleting a circuit through /S and its 
armature as long as H is deenergized. 
This circuit now through S is inde- 
pendent of the signal and will con- 
tinue even though the signal goes to 
the stop position. 

A train moving from right to left 
will deenergize relay T in section B, breaking the circuit through 
H and allowing the signal to go to stop. As the signal will 




262 RAILWAY SIGNALING 

be in the stop position before the train enters section A, the 
stick relay S will not be energized. In (B), when a train moves 
from left to right, the control relay H for signal 2 becomes 
energized by means of wire X as soon as the train passes signal 
4. The wiring is so arranged through a polarized relay that 
signal 2 then goes to the 45-degree position. When the train 
reaches M, 4 will go to the 45-degree position and 2 to the 
90-degree position. 

Figure 282 shows the wiring for two sidings with an absolute 
and a permissive signal at each end and two pairs of intermediate 
signals opposite each other. 



^ ■ V 



X \ 



I . o 3 . o 5 . „ 7 , 9 , n M , n 13 

V ^ ^ i I 



\ ^ ^ 



Diagram showins Head on' Controls only 



O1A6RAM SHOWIN6 'Following* Controls only 

A B C 

Diagrams 3 and 3a. 
Fig. 279. — Signal control and location diagram for the A. P. block system. 

Figure 283 is a typical plan of the A. P. Block System installed 
on 20 miles of single track on the Puget Sound Electric Railway 
operating between Seattle and Tacoma, Wash.^ It is a double- 
rail return system with 600-volt direct-current power for pro- 
pulsion. The passing sidings average about 23-^ miles apart. 
There is a starting signal for traffic in each direction located at the 
passing track, and there are two intermediate signals between 
sidings. From the 60-cycle, 2,200-volt, transmission line, the 
current is stepped down to 110 volts for signal circuits. The 
signals operate in three positions in the upper left-hand quadrant. 

168. Other Installations. — Figure 284 represents a typical 
wiring diagram of a 37-mile installation of alternating-current 

1 Proceedings, Railway Signal Association, 1915. 



AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 263 



Z ' 4^ ' 6^ „ 8'~ ' 10' ' 12 ' ' 14 

I I I I I li * Ml N I I I I 1- 

I , 3 , ^5 _7 , 9 , II , 13 

SB fe> ^ ^ Csi E2> fe> 

** "* DIAGRAM N9 4 "^ 



^ ' 4*^^ ' fi^"" ^ 7 10 ' 12 ' 14 

, I , 3 , 5 , 7 , 9 , U , 13 

T ^ ^ "~^ —^ —^ ^-fe> 

DIAGRAM NS 5 



^ .%^ 



4 — ■ 6 ■__i_ir' lo"^ — ' 

> < I I I I ^ i I t ^ \ I I 

I, _3 , 5 , 7 , 9 

DIAGRAM N9 6 



2 -^ 4 ' B ' ^ • " 10 • 12 

^ 1 -*-^m-^ III / I ^ 1 I I I I I 

, I , 3 , 5 ^ 7 ' , 9 II , 13 

A DIAGRAM NO 7 



2^ ' 4^ ' 6^ ' — ^ 10^ ' 12^ ' 14 

.»s^»i 1 1 I I 1 •" N — ^— I 1 1 1- 

I . 3 . 5 ^ 7 . 9 . II _ 13 



DIAGRAM Ne 6 



■E 



e -"— ' 4^^ 6^ ^___l__r^ 10^ ' 12^ ' 14^^ 

^ii» I 1 1 1 1 t ^ N 1 1 I I ^B l " ^ 

_„l , 3 , ^5 , 7 9 II 13 

T -^> ^ ^ T ^ ^ 

DIAGRAM N9 9 



„ 2^ ' 4^ ' ^ , ^~ ^ 10^ 12^ ' 14 
N I 1 I 1 I — ^ 1 ^ "^ 1 <■ — I I 1 y 



_5 7 9 

^ ^ T 

DIAGRAM N9 10 



j^- ,-^~ «'^— , 8^ ,„V_ ^< 

1 I I 1 I l "^ ^ "^ i 1 *-^ 

I , 3 5 7 9 II 

— fe> *^ ^ "^ T 

DIAGRAM NS II 
Fig. 280. — A. P. block system diagrams. 



264 



RAILWAY SIGNALING 



signaling on the N. & W. Ry.^ The circuits are the "T. D. B.'' 
type with such modifications as are required for local conditions. 
The bracket signals at the ends of passing tracks are absolute 
signals; all others are permissive. The signals operate with a 
25-cycle single-phase current fed by a 4,400-volt separate trans- 
mission hne from the power house. They are lighted by 1 10- volt, 
10-watt carbon filament lamps. There are two bulbs in each 
lamp, one burning continuously, with a relay to cut in the second 



+^ 



+^ 



fe ! 





(A) 



1 1- 



^ 




Fig. 281. — A. P. block system circuits. 



in case of failure of the first. The blocks between passing sidings 
are approximately 4,500 ft. long. Model 15 polyphase vane two- 
position relays with 110-volt local current and 4- volt track 
current are used on all track circuits. Polarized line circuits 
operate with Model 15 polyphase vane type of relays having 
110-volt line and 110-volt local current. All other Hne circuits 
operate with vane type of relay. 

1 Proceedings, Railway Signal Association, 1917, page 448. 



II 



AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 265 



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266 



RAILWAY SIGNALING 



Figure 286 is typical of the automatic signal installation 
on the electrified portion of the C. M. & St. P. R. R. in Montana. 
The signal system is fed by a 4,400- volt single-phase line carried on 
the trolley poles. This current is obtained from the 2,300/4,400- 
volt step-up transformer on the secondary side of the power 
transformers that feed the motor-generator sets at the substations, 
which are located about 35 miles apart. The 2,300-volt current 





Fig. 283. — A. P. block system on the Puget Sound Electric Railway. 



for these sets is stepped down by transformers from the 100,000- 
volt power transmission line. The 2,300/4,400-volt step-up 
transformer is a 25 k.v.a., single-phase, 60-cycle transformer. 
The 4,400- volt winding feeds the signal circuits on each side of the 
sub-station. Each signal circuit is controlled by a 200-amp., 
4,500-volt oil switch so that failure or other troubles will be 
limited to comparatively short sections. Each sub-station in 
the automatic signal territory is equipped with transformers, 



AUTOMATIC BLOCK SIGNALING ON SINGLE TRACK 267 




268 



RAILWAY SIGNALING 




AUTOMATIC BLOCK SIGNALING ON SINGLE BLOCK 269 

switches, relays, recording and other apparatus shown in Fig. 
287 for controUing the 4,400- volt signal Hne. 

The transformers step the current down from 4,400 volts to 
110 volts, 60-cycle, single-phase current for signal and other pur- 
poses; while track transformers step the current from 110 volts to 
1-18 volts. The track circuits are the double-rail return system 
with end feed when the length does not exceed 7,500 ft., and with 
center feed when they do exceed this distance. The relays are: 




Fig. 286.- 



- Arrangement of apparatus at double signal location, C. M. & St. P. 
Ry. {Froceedings, R. S. A., 1917.) 



Model 15 vane type, 60-cycle, single-phase, two-element, two- 
position, for track circuits; and Model 15, two-element three-posi- 
tion, vane type, both simple and slow-releasing, and Model 15, 
single-element, two-position vane type, operating as a stick relay 
for line circuits. The normal voltage for the rail element of the 
track relay is about 1 volt, while that for the local element is 
110 volts. Where the maximum grade does not exceed 1.6 
per cent., impedance bonds of 500 amp. capacity with direct- 
current resistance of 0.0014 ohm are used; and where the grades 



270 



RAILWAY SIGNALING 



exceed this value, bonds of 1,500 amp. capacity with direct- 
current resistance of 0.0003 ohm are used. The signals are 



To Transformer 
/V<7 / 



7b Trans farrrjgi^ 




TraJiJ formers . 






ArresferJ 2^, 



ir^i 



Fig. 287. — Typical substation wiring for feeding signal circuit on C. M. & St. P. 
Ry. (Proceedings, R. S. A., 1917.) 



three-position color-light type for giving both day and night 
indications.^ 

^ Proceedings, Railway Signal Association, 1917, and Signal Engineer, 
September, 1917. 



CHAPTER XV 
SIGNAL MECHANISMS 



TWO-POSITION SIGNALS 

169. Hall Disc Signal. — The Hall disc signal consists of a 
cloth disc 17 in. in diameter for giving day indications and a lamp 
with a glass or roundel 63-^ in. in diameter for giving night 
indications. The disc and roundel are mounted on aluminum 
arms that are fastened to the Z-shaped armature of an electro- 
magnet as shown in Fig. 288. The 
larger disc is made by fastening a 
piece of cloth over a wire hoop, a 
red cloth being used for home 
signals and a yellow or green cloth 
for distant signals. The day stop 
or caution indication is given by 
exposing the full disc to the view of 
the engineman; the proceed indica- 
tion is given by withdrawing the disc 
from view, showing in its stead the 
white background on the inside of 
the signal case. The night stop or 
caution indication is given by hav- 
ing the red or green roundel stand 
in front of the signal lamp; the pro- 
ceed indication is given by having 
the roundel swing aside exposing the 
lamp and giving a white light. 

The signal is moved to the clear 
indication when the Z-shaped arma- 
ture that supports the colored discs is rotated between the poles 
of an electro-magnet as shown in Fig. 289. The ''hold clear" 
mechanism is made up of a set of high resistance coils whose arma- 
ture is a flat bar fastened to the Z armature of the clearing coils. 
Just as the clearing coils pull the disc to the complete clear 
position they operate the circuit breaker to place the clearing 
and the holding coils in series. The total resistance diminishes 

271 




Fig. 



288. — Hall disc signal 
mechanism. 



272 



RAILWAY SIGNALING 



the flow of the current to the minimum necessary to hold the 
signal clear, for it requires much less current to hold the signal 
clear than it does to operate it. In the normal clear system the 
signals stand cleared except when the block is occupied by a train. 
The operating mechanism is all enclosed in a combination metal 
and wooden case mounted on top of a pole of suitable height. 



(F/ass Disc 





Pole Pieces 



Cloth D/sc 



Fig. 289. — Electro-magnets and Z-armature. 

170. Union Style "B" Signal.— Figure 290 shows the operating 
mechanism for a Union Style ''B" two-position signal where the 
home and distant signals are on the same mast. The motor, ilf , 
connected in the signal circuit has on the end of its armature 
shaft a small pinion, which by means of a train of intermediate 
gears, drives an endless chain, 10. This has in one of its links 
a trunnion, 12, that under certain conditions lifts a slot arm. A, 
to which is fastened the up-and-down rod, 6, that operates 
the signal blade. The slot arm is pivoted near the right-hand 
end. When the electro-magnet, 7, on the slot arm is energized, 
the arm becomes rigid, and as the motor armature rotates, the 
trunnion lifts the fork-head, 5, of the slot arm and clears the 
signal. When the arm reaches the height where the signal is 
fully cleared, the lugs on the sides of the fork-head, 5, are caught 
by the hOoks on pawl 24 and the signal is held in the clear posi- 
tion. The top of the slot arm makes contact with 30, breaking 
the circuit to the motor and making contact for closing the circuit 
to the distant signal. 

The distant slot magnet is made with two windings about the 
same core, one a low-resistance winding in series with the motor 
to energize the magnet and yet allow a sufficient amount of 
current to flow to the motor, the other a high-resistance winding 
in multiple with the motor to keep the magnet energized when 



SIGNAL MECHANISM 



273 



the motor is cut out and yet reduce the amount of current, for 
less is required when used only for holding purposes. A wiring 




Fig. 290. — Style "B" two-position signal mechanism. 

diagram for direct-current control is shown in Fig. 291. The 
signals stand at the proceed position except when the block is 



ll 



I 

I 







Disfant^lot/lrm 


1 








~T=1 II 1 — ' 

L^ High 












HomeSlci-/lrm 




, 


H — 1 


If " 


1 






Track^XX ^ 




—l^ 










^ 



NOTE'. Contact /opens and 2 and 3 clo^e 
just as the home signal reaches 
^hp full clear positjon 

Fig. 291. — Wiring diagram for style "B" signal when operated by direct 
current and controlled by polarized relay. 

occupied by a train. When the slot magnets become deenergized, 
the armature, T, falls away by gravity releasing i/, TFand L, Fig. 

18 



274 



RAILWAY SIGNALING 




Fig. 292.— Style "B" slot arm. 



PistanfSlof/lf-m 




Distant Control 
Common 



Home Control 



NOTE: Contact 1 opens and 2 anc^ 3 close 
Just as the home signal reaches 
the full clear positjon 



Fig. 293. — Wiring diagram for style "B" signal when operated by alternating 

current. 



SIGNAL MECHANISM 



275 



292, thereby destroying the rigidity of the arm and allowing the 
signal to go to the normal position by gravity. The dashpot 
on the rear of the machine serves to diminish the shock of the fall. 
There are two sets of chains operated by the same motor, one to 
clear each signal arm. Figure 293 is a wiring arrangement when 
the signal is operated by alternating current instead of direct 
current. 

THREE-POSITION SIGNALS 

171. Union Electro-pneumatic Signal. — Figure 294 illustrates 
the principle of three-position semi-automatic signal movement 




Fig. 294. — Diagram showing the operation of three-position semi-automatic 

signals. 

controlled by both electro-pneumatic interlocking and polarized 
track circuits. While there is a valve and magnet for both 
45- and 90-degree positions, the air supply from the main comes 
only to the 45-degree valve. The supply for the 90-degree 
position comes from the 45-degree cylinder, an arrangement 
which insures that if the air or current to either the 45- or 90- 
degree positions should be cut off, the signal would recede from 
the vertical to the caution or stop position respectively. 

172. Union Style "S'» Signal.— The Style ''S" mechanism 
shown in Fig. 295 is an outgrowth of Style ''B" to meet the 
requirements of three-position signaling. The equipment may 



276 



RAILWAY SIGNALING 



be designed to operate with either direct or alternating current. 
It has only one slot arm, but it has two fork-heads and operates 
with two chains. The lower chain raises the arm from the stop 
to the caution position, and the upper one from the caution to 
the proceed position. 




Fig. 295. — Style "S" D.C. motor mechanism. 

173. Union Style "T-2" Signal.— The Union "T-2" top-post 
three-position upper quadrant signal is made to operate with 
either a direct-current or an alternating-current mechanism. 
The direct-current equipment, shown in Fig. 296, consists of an 
electric motor that drives a train of gears to operate the sema- 
phore shaft, a direct-current controller, and an appliance for 
holding the signal in the proceed or caution position. The 
holding mechanism is placed at the outer end of the armature 



SIGNAL MECHANISM 



277 



shaft. It consists of a ratc^het connection, shown in Fig. 297, 
that engages the shaft only when the motor is moving the 




Fig. 296. — Style "T-2" D.C. signal mechanism. Parts cut away to show 

construction. 

semaphore to the caution or the clear position. ' Connected to the 
ratchet are three stop blades held by the drum 5. Directly below 




E F 

Fig. 297. — Diagram of style "T-2" D.C. signal mechanism and parts. 

the stop drum is the slot magnet constructed very much like the 
pin valve used in electro-pneumatic mechanisms. When the 
magnet is energized, arm 42 is raised carrying with it the steel 



278 



RAILWAY SIGNALING 



roller, 15, and the contact finger 41, closing the motor circuit at 
20. As the stop drum rotates, the blades come in contact with 
the roller stopping the drum, but allowing the armature to turn 
on account of the ratchet. When the motor is clearing the 
semaphore, the ratchet does not engage with the pawls in the 
stop-drum and consequently it does not revolve, being prevented 
from doing so by one of the stop blades coming in contact with 
roller 15. When the slot magnet is deenergized the arm 42 drops 
by gravity. When the signal blade drops to the caution or 




Fig. 298. — Mechanism wiring for low voltage style "T-2" signal. 



stop position, it runs the motor backwards generating a current 
that it drives through a resistance coil, thus retarding the motor 
and relieving the shock as the blade comes to rest. 

Figure 298 represents the mechanism wiring for a direct- 
current signal to be operated by a current with less than 30 
volts. The circles, numbered from 1 to 8, represent the contact 
segments of the circuit controller. 8 controls the motor circuit, 
7 brings the slot under the control of the 90-degree control relay 
when the semaphore arm is at the caution position, and 1 prevents 



SIGNAL MECHANISM 279 

this relay from energizing until the signal reaches the caution 
position. 

The signal arm is moved from the stop to the caution posi- 
tion by first energizing the slot magnet 19 through the 45-degree 
control wire A, segment 7, wire B, low-resistance winding of the 
slot coil, wire C, contact 22, wire D, motor, and common wire. 
The slot thus energized raises finger 41, which opens contact 22 
and places the high- and low-resistance coils in series with wire 
E. This circuit complete to the common wire holds the slot 
energized, closing contact 20 and thereby completing the motor 
circuit through wire D, wire G, and segment 8, to wire F. When 
the semaphore arm reaches the caution position, segment 8 
opens the circuit to the motor, but the slot remaining energized 
by another route will retain the signal in this position. 

The semaphore arm is moved from the caution to the proceed 
position by energizing the 90-degree control relay through segment 
1. The current then flows through wire H instead of through wire 
A and segment 7, for 7 opens in the first movement of the sema- 
phore arm towards clearing. Another contact on the relay 
closes the motor circuit through wire I and the lower contact on 
segment 8. This segment opens when the semaphore arm reaches 
the proceed position, but the coil serves to hold the arm in this 
position the same as it did in the 45-degree position. The 
jumpers P and Q, are added only for two-position signaling, 
to 90 degrees. 

When the control circuits are broken the slot magnet becomes 
deenergized. The blade falls and the motor becomes a generator. 
The back point of finger 41 makes contact at 21 closing the local 
''buffing circuit" to the motor through wire D, finger 41, resis- 
tance 38, and wire E. The generator driving its current through 
the resistance 38 thus acts as a brake at both the 45- and 90- 
degree positions of the semaphore arm. If only the 90-degree 
control relay is deenergized, the slot will be released until contact 
7 is closed. The 45-degree control circuit will then retain the 
signal in the caution position. 

174. General Railway Signal Model "2A" Signal.— Figure 
299 shows the General Railway Signal Model "2A," top-post 
mechanism for a three-position upper quadrant signal. The 
signal is made with either a direct- or an alternating-current 
mechanism. The direct-current motors are made to operate 
on either a low voltage, 8, 10, and 20 volts, or a high voltage. 



280 



RAILWAY SIGNALING 



110 volts. Formerly, the alternating-current mechanism voltage 
varied from 55 to 220, but more recent practice employs induc- 
tion motors with a voltage of 110. 




Fig. 299. — Model 2 A, top-of-mast mechanism. 

The most common low-voltage direct-current type of equip- 
ment is made to operate at 10 volts with a current of 2 amp. 
It is equipped with a four-pole series-wound motor. The hold- 
clear mechanism is shown in Fig. 300. 
This retaining mechanism is actuated 
by a compound-wound electro-magnet 
whose armature operates a pawl that 
meshes with a toothed disc on the 
motor shaft. One set of the windings, 
having a resistance of 26 ohms, is the 
pick-up coil; while the other set, hav- 
ing a resistance of 630 ohms, is the 
retaining coil. In the case of the 
10-volt machine, 0.25 amp. is required 
to pick up the armature, but only 
0.016 amp. is necessary to hold it and 
hence retain the motor in the caution or 
clear position. The circuit controller 
makes a contact just before the signal blade reaches the 45-degree 
and 90-degree positions energizing the pick-up coil and picking 




Fig 



300. — Retaining mech- 
anism. 



SIGNAL MECHANISM 



281 



up the hold-clear armature. A second contact throws the pick- 
up and holding coils in series making a total resistance of 656 
ohms. As the signal stands at the proceed position in the normal 
clear circuit except when a train is in the block, the current is 
flowing through the coils a very large portion of the time, and 





the high-resistance winding is used to reduce the amount of 
current to a minimum. 

As soon as the track relay becomes deenergized by a train, 
the holding coils become deenergized also, and their armature 
falls away by gravity allowing the signal to drop to the caution or 



282 



RAILWAY SIGNALING 



stop position. The force of the faUing signal arm is checked by 
driving a current through a resistance coil. As the blade drops 
it operates the gears and the motor in a reverse direction from 




that used to place the signal at caution or clear. This backward 
movement of the motor makes it a generator; and just before 
the blade reaches its caution or horizontal position, this generator 



I 



SIGNAL MECHANISM 



283 



drives its current through the resistance coil, checking the fall of 
the blade, thereby preventing damage to the equipment. 
Figure 301 shows the wiring diagram for low-voltage direct- 
current control of an automatic signal while Fig. 302 shows it 
for alternating-current control. 




Fig. 303. — Style "K" signal. 



175. HaU Three-position Style "K" Signal.— The Hall Style 
"K" three-position signal is made with either a direct- or an 
alternating-current mechanism. Figure 303 represents the top- 
post type built with direct-current equipment. The motor 
operates on a vertical axis and drives the signal arm by means of 
a series of gears. Gear B, Fig. 304, is attached rigidly by screws 
to the hold-clear clutch magnet G. The armature M, of this 
magnet is supported on a separate shaft from the gear B and 
magnet G and rotates independently of them. The blade is 
held in the caution or clear position by energizing the magnet G 
causing a friction contact between the magnet surface and the 
outside bronze rim on the armature. The motor armature is 
held from rotating in the reverse direction by means of the brake 
N, Fig. 305. A train coming into the block will deenergize the 



284 



RAILWAY SIGNALING 



magnet and allow the blade to drop to the caution or stop 
position. 

Two governors, 0-0 fastened to the armature M, revolve with 
it and as the speed increases due to the fall of the blade, the 
governors swing out by centrifugal force and engage against 
the under surface of I, a stationary portion of the hold-clear 
magnet. The tendency of the blade to increase its speed as it 
falls, serves to exert a pressure by the governors to hold it in 
check. 

The magnet is shown partly in section in Fig. 304. U is the 
winding and T is the core. The core is fastened to an outside 
shell connected with the insulated piece W, the bottom of which 
at / serves as a friction contact for the governors, 0-0, The 








■{^ at'r ^J» 



Fig. 304. — Operating mechanism for style "K" signal. 



brass rings, X, serve to connect the terminals of the magnet 
winding with the outside battery through two brushes, one on 
each ring. In order to prevent such injury to the mechanism 
as comes from stopping suddenly, there is a ratchet appliance to 
permit the motor to continue to run after the blade comes either 
to the caution or stop position. 

176. HaU Style "L'» Signal.— The motors of the Hall Style ''V 
signal are made to operate on either 8 or 110 volts direct current 
or on standard voltages and frequencies of alternating current. 
Figure 306 represents the top-post mechanism constructed with 
direct-current equipment. The motor is a bi-polar series type 
operating on a horizontal axis. Its power is transferred to the 



SIGNAL MECHANISM 



285 



signal arm through a train of gears driven by a small pinion 
secured to the motor spindle by means of a double cone slip 
clutch. 

The hold-clear mechanism is located in front of the motor 
and consists of a latch lever in which is a spring actuated latch 
dog shown in (A), Fig. 307. 
One end of the lever is piv- 
oted on the bearing frame, 
and the lever itself is free to 
swing downward. As the 
hold-clear magnet becomes 
energized after the signal 
arm comes to the desired 
position, its armature lifts 
the latch lever until the latch 
dog engages with one of the 
rollers mounted in a support 
flexibly connected to the outer 
end of the motor spindle . This 
prevents the mechanism from 
backing up. 

The controller consists of 
two spindles so geared to- 
gether that when they are 
operated by the pinion that 
is connected to the main gear 
spindle they will move sim- 
ultaneously. These spindles 
carry hubs on which are 
mounted contact cams, one 
of which is shown in (B), Fig. 
307. A snubber is provided 




Fig. 305. 



- Operating mechanism 
style "K" signal. 



for 



to relieve the shock when the signal arm drops to the 45 and 
positions. 

177. Federal Three -position Type "4" Signal.— The Federal 
Type ''4" signal is provided with an electric motor of suitable 
characteristics to adapt it for use on direct currents of varying 
potentials from 8 to 110 volts or on alternating currents of 
110 and 220 volts with the usual variation in frequency which 
may be encountered. 

Figure 308 represents a 10-volt direct-current top-post mechan- 



286 



RAILWAY SIGNALING 



ffi 




SIGNAL MECHANISM 



287 



ism. By a train of gears the motor drives the blade to the 45- 
and 90-degree positions. When the semaphore spindle has 




Fig. 307. — Hold-clear mechanism and circuit controller for style "L" signal. 

reached a position corresponding to proceed, the circuit through 
the motor is interrupted and a circuit through the hold-clear 




Fig. 308. — Federal type "4" top-post signal mechanism. 

magnets is estabhshed. The hold-clear magnet for 10-volt 
direct-current operation is generally wound to a resistance of 



288 RAILWAY SIGNALING 

500 ohms. As th^ hold-clear magnet, DZ, becomes energized, it 
attracts the armature EJ supported by the arm EF. This causes 
a detent roller or dog to engage with teeth on a member attached 
to the motor shaft in such a manner as to prevent the motor 
from rotating towards the stop position, as long as current flows 
through the hold-clear coils. 

AUTOMATIC STOPS 

178. Motor-Operated Automatic Stops. — The motor-operated 
train-stop, shown in Figs. 309 and 310, was designed for use on 
lines of the New York Municipal Railway Corporation operating 
in and between New York City and Brooklyn. It is installed 
between the rails of the track and is operated by a separate tripper 
arm through the medium of a rocking shaft that may be connected 
to either side of the operating mechanism. The trip arms are 
made of cast iron so designed that they will break if any unyielding 
portion of the train happens to strike them, but not when the 
train trip arm strikes them. The circuit breaker is operated 
directly from the main shaft of the stop, as the drawing indicates. 

The stops on these lines are used in connection with all signals 
except dwarfs at interlocking plants, and are governed by the 
indication of the signals. When a signal is in the stop position, 
the tripper arm stands above the rail; and if a train attempts to 
pass the signal set in the stop position, the arm engages a valve 
that opens the air line on the train, applies the brakes and stops 
the train. When the signal is clear, the arm drops below the top 
of the rail. 

LIGHT SIGNALS 

179. General. — Color-light signals are built for long- and 
medium-range outdoor service and for short-range indoor service ; 
while position-light signals are built only for long- and short-range 
outdoor service. The long-range signals are used for high-speed 
trains and involve considerable accuracy in construction and in- 
stallation. They require highly concentrated filament lamps for 
condensing the light and accurate lenses for projecting it. As 
such exacting service is not required of the short-range signals, 
their construction is somewhat simplified. Concerning long-range 
signals, the following paragraphs are taken from the 1917 Pro- 



ceedings of the Railway Signal Association: 



fL U/llC 0.1,0/11 VVO/J kJl^llCtl ^i.>30Wt^lC<,VJlV/lX . 

iPage 8. 



SIGNAL MECHANISM 



289 





19 



290 



RAILWAY SIGNALING 



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SIGNAL MECHANISM 291 

''In broad daylight, under unfavorable sun and background condi- 
tions, there are two alternatives open for the hght source: Either a 
very high wattage lamp must be used, or a lower wattage with a con- 
centrated and accurately located filament. (As illustrating the re- 
markable influence of concentrating the light source, we refer to the 
April and May, 1914, numbers of the Signal Engineer, where this subject 
is fully treated. Figure 24 shows that a 24- watt concentrated filament 
lamp gives a peak candlepower of 65,000, and the same wattage in 
commercial lamp gives 500 candlepower. To get a long-range indica- 
tion, it is necessary to project a beam candlepower of 5,000 or 6,000.) 

''The concentrated filament requires an accurate basing of the lamps 
so that they may be interchanged without disturbing the alignment 
of the signal. The automobile headlight requires refocusing when a new 
lamp is put in place. This cannot be done with the light signal. It 
would involve too much work and would also involve the employment 
of two experienced men to take care of realignment whenever a lamp 
burned out. Moreover, it is difficult, if not impossible, to obtain any 
very accurate adjustment for maximum candlepower in the field. Such 
work is properly done in a dark room. The lamps for high-speed signals 
are, therefore, rebased in a special jig, which permits the accurate 
location of the base with respect to the filament. 

"If a commercial concentrated filament lamp were to be used, the 
diameter of the filament would have to be increased to allow for commer- 
cial variations in lamp manufacture. It might be possible to design 
a lamp filament having sufficient concentration and yet having area 
enough to permit commercial variations, but, as these commercial 
variations permit nearly 3^-in. departure in all directions from a theo- 
retical filament location, the lamp wattage would have to be increased 
eight or nine times at least to maintain the same degree of concentration 
and consequently the same candlepower. 

"The long-range signal has a very small beam spread, on account of 
the concentrated filament employed. Consequently, these signals have 
been designed to facilitate accurate alignment by providing separate 
horizontal and vertical adjustments. When it is still necessary to provide 
some means of increasing the spread to take care of curved track, a 
prism lens, which spreads or "fans" the light in the horizontal plane, 
but which does not increase the vertical spread, is used, and the hght 
is projected in the most efficient manner possible (see page 131 of the 
May, 1914, Signal Engineer). By means of this prism, the maximum 
possible range on curved track is secured with the minimum possible 
expenditure of power." 

COLOR-LIGHT SIGNALS 

180. Long-range Type. — This type of signal is used principally 
on steam and high-speed electric roads. A doublet lens is 



292 



RAILWAY SIGNALING 



employed in order to utilize to better advantage the rays of 
light from the lamp. The outer lens is made of clear glass from 
8% to 10 in. diameter with approximately 4 in. focal length. 
The inner lens is colored and is generally 5J^ in. in diameter 
with a H ill- focal length. 

Figure 311 shows the Union Style L, three-position long- 
range colored-light signal installed on the electrified portion of 




Fig. 311. — Front and back views of Union style "L" light signal. 

the C. M. & St. P. R. R. The range of vision on a tangent 
varies from 2,500 ft. when the sun is shining directly on the lens 
to 4,000 ft. under more favorable conditions. The three outer 
doublet lenses, each 8>^ in. in diameter, are provided with an 
individual hood over each lens. The bottom lens gives the stop 
indication, the middle one caution, and the top proceed. The 
main lamps for lighting signals are 6-volt, 28-watt, with con- 



I 



SIGNAL MECHANISM 



293 



centrated filament. On tangents, lenses having a spread of 3 
degrees were used, but on curves deflecting prisms of 10 or 20 
degrees were used depending upon the amount of curvature of 
the track and the length of view. A metal background extend- 
ing entirely around the hood was provided for each signal to 
intensify the signal indication. 

Figure 312 shows a double light signal installed on the Union 
Traction Company of Indiana by the General Railway Signal 
Company. The signals governing in each direction are mounted 




Fig. 312.— a. P. B. light signal. 



back to back on a bracket on the same pole. The upper case 
houses the red and green lamps and the lower the yellow or 
permissive lamp. This signal is used in the "Absolute Permissive 
Block System/' the red being the absolute indication for opposing 
movements and the combination of red and yellow being the 
permissive indication for following movements. 

181. Medium -range Outdoor Type. — The medium-range sig- 
nal is provided with a simpler lens, generally 5% in. in diameter. 
The three-position signal shown in Fig. 313 is lighted with two 36- 
watt 110-volt tungsten lamps connected in multiple. It has a 
range of vision approximately 1,500 ft. under adverse conditions 
of sunlight and 2,500 ft. at other times. The design is compara- 



294 



RAILWAY SIGNALING 



tively simple and the signal is used on medium-speed interurban 
and elevated lines. 

Figure 315 is a detail of the interlocking signal shown in Fig. 
314 and used on the subway and elevated lines of the New York 
Municipal Railway Corporation. The signal is semi-automatic, 
lever-controlled, and has two pairs of lights with three in each 




Fig. 313. — Union Model "N" light signal. Rear view. 



pair that serve the same purpose as a two-arm semaphore signal. 
Five-in. doublet lenses with a 30-watt lamp behind each lens, are 
used on the elevated hues. The subway signal is an exact duplicate 
of the elevated type, except that a plain lens and a 10-volt 12-watt 
lamp is used. An emergency signal referred to as a calling-on 
signal is mounted just below the lower lens of this double signal. 
When this calhng-on signal is displayed the words ''Proceed at 
Caution" are illuminated. The calling-on signal is always 



SIGNAL MECHANISM 



295 



displayed with two red lights showing above and means that the 
motorman is to press the emergency pushbutton located on the 
side of the signal. This push-button is used to clear the stop 



6reen Q) 



Yellow 
Red 

Green 

Yellow 

Red 



r^ 



Push 
duffon^ 



m 



• 



stop and Skiy 



2.5 4 

Key Automatic Proceed Caution Proceed Caution 

Stop. Proceed over diverging eli verging rou te 

expecting to find route expecting Automatic 

Block occupied to find nex t dioclr Clear 
Signal Red 

SEMI-AUTOMATIC INTERLOCKING SIGNAL 



' Proceed Caution 
over main route 
expectina tofirid 
next Signal Red 



6 

Proceed 



Green 
Yellow 
Red 



7 8 

Sfofl Ke Y Automatic Stop Proceed Cau Hon expecting 

and Proceed expecting to final next Signal Red 
to find Block occupied. 



9 

Proceed 



AUTOMATIC 516NAL5 



Yellow 
Red 



• 



10 
5fop andSta^ 



W 

Proceed Caution 



INTERLOCKING DWARF SIGNALS 

Fig. 314. — Signals used on lines of New York Municipal Railway Corporation. 

{General Railway Signal Co.) 



in case of an emergency when the signal apparatus fails or when 
it becomes necesary to use the calling-on signal. After the 
motorman clears the automatic stop he proceeds slowly expecting 
to find the block occupied or to cross over to another track and 



296 



RAILWAY SIGNALING 




< — 

Foundorhon Plan 
Fig. 315. — Interlocking signal shown in Fig. 314. 



SIGNAL MECHANISM 



297 



move against the normal direction of traffic. A rear home signal 
is used on these lines for the same purpose as a distant semaphore 
signal. It is a standard single three-indication signal, semi- 




FRONT VIEW 



Fig. 316. — Subway and tunnel signal. (Union Switch and Signal Co.) 



automatic in its operation. The dwarf signal used at interlocking 
plants is a non-automatic two-indication signal. 

182. Short-range Subway and Tunnel Type. — Subway and 
tunnel signals are simple in design since there is no need of protec- 



298 



RAILWAY SIGNALING 




(A) Signal lamps, background omitted. 




(B) Details of signal lamp. 
Fig. 317. — Position-light signal. (Union Switch and Signal Co.) 



SIGNAL MECHANISM 



299 



tion against sunlight. The hood is unnecessary, the lenses are 
small, and the lights require less current than the outdoor type. 
Figure 316 shows the type of signals installed in the Boyleston 
Street Subway of the Boston Elevated Railroad. Each lens has 
behind it two 4- c.p. 55-volt tungsten lamps. 

POSITION-LIGHT SIGNALS 

183. Long-range. — The position- or beam-light signals have 
lenses that are yellow tinted. The range of vision averages about 
2,500 to 4,000 ft. for high-speed signals and about 1,000 ft. for 
dwarfs. Of the three rows of lights shown in Fig. 317 represent- 





1 

i 





Fig. 318. — Position-light dwarf signal. 



ing the three positions of the upper blades in upper quadrant 
signaling, only one can be illuminated at a time. The selection 
is done by a three-position relay operating in the same manner as 
for a semaphore signal. The lights in the lower portion of the 
signal, Fig. 319, correspond to the lower blade of a two-arm 
semaphore, and the combination of the two sets is used to carry 
out the more recent aspect scheme of the Railway Signal Associa- 
tion for block signaling and interlocking. The four 12-volt 
5-watt lamps in each row are spaced 18 in. on centers and are 
equipped with 5%-in. inverted toric lenses, as shown in (B), 
Fig. 317. The same voltage is used for both day and night 
indications. The glass reflector placed at an angle just above the 
lamp tends to throw the light downwards and assists in giving 
a good short-range indication. Each lens is covered with a 
deep hood to protect it from the sunlight. 



300 



RAILWAY SIGNALING 




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SIGNAL MECHANISM 301 

184. Short-range or Dwarf. — The dwarf is made with two 
Hghts in each row giving the three indications of a semaphore 
blade in upper quadrant signahng. As the range is shorter, the 
lenses are not so large and the filament adjustments are not so 
accurate. 



CHAPTER XVI 
HIGHWAY CROSSING SIGNALS 

185. General. — In these days of extensive highway travel, it 
has become the practice to install signals at grade crossings to 
give warning of the immediate approach of trains. This has 
become practically a necessit}^ since the advent of the automobile, 
for it is the common occurrence now for persons to start across 
country on an overland journey of hundreds and even thousands 
of miles crossing railroad tracks that they have never seen nor 
heard of before. It was different in earlier days when all such 
travel was by buggy or wagon where one seldom went more than 
12 or 15 miles from home and knew the details of every railroad 
crossing within that section. The busiest crossings in the cities 
are protected by flagman and by gates; but it is impractical to 
watch every crossing, especially those in outlying and country 
districts. 

Both visible and audible signals have been installed to meet 
this need. The visible signals are constructed with a plain 
light, a flash light, a moving light, a wigwag arm, or combinations 
of such methods of giving indications. On account of the 
increase in travel by automobile aiid motorcycle with their 
attending noises, the visible signal seems to meet the requirement 
better. Besides, more and more of the automobiles are made 
enclosed, especially for winter service. The audible signal is 
essentially the ringing bell. Many manufacturers are making 
use of both visible and audible signals, combining them in one 
signal for both day and night indications. 

186. Highway Crossing Signals. — Figure 320 represents the 
Union Three Aspect Automatic Flagman. When a train 
approaches the crossing where such a signal is installed, the red 
banner swings across the road to give warning. The banner 
carries a red hght and has the letters S-T-O-P painted across the 
face of the disc. The red lamp is lighted only when the banner is 
in motion. When there is no train approaching the crossing, 
the banner is concealed between the two metal screens which 

302 



HIGHWAY CROSSING SIGNALS 



303 



bear the words ''Look/' ''Listen." On top of the post is a gong 
type of bell that rings while the banner is swinging. 





Fig. 320. — The Union three aspect automatic flagman. 



The operating equipment consists chiefly of electro-magnets, 
two pairs of which are operating coils that swing the arm and 
one pair is a set of holding coils that retain the arm between the 
screens. The flagman operates on a 
local circuit of 10 volts direct current 
requiring 0.4 amp. to swing the arm 
and 0.4 to light the 5-watt, 12-volt lamp. 
The holding coils are wound with a re- 
sistance of 1,000 ohms, thereby reducing 
to a minimum the amount of current 
consumed while the signal is giving the 
clear indication. The lamp attached to 
the banner can be either fixed or oscillat- 
ing. The fixed lamp can be so arranged 
with an oil burner as to give flashes of 
light as the arm swings back and forth. 

Figure 321 is a highway crossing signal 
having a crossing sign, a wigwag signal, 
and a locomotive type of bell. The 
signal gives warning by ringing the bell 
and by waving at right angles to the 
highway, the red wigwag disc, which is 26 
in. in diameter. When the signal is in 
motion, the red lamp in the center of 
the disc and the words "DANGER," 
"STOP," are all illuminated both day and night to intensify 
the indication in giving the warning of an approaching train. 




Fig. 321. — Wigwag cross- 
ing signal. (Railroad Supply 
Co.) 



304 



RAILWAY SIGNALING 



The bell ringing at the same time the wigwag is active is an 
additional means of calling attention to the movement of the 
train. 

Figure 322 shows the locomotive bell. The operating mechan- 
ism in (A) is a solenoid electro-magnet. As the magnet becomes 
energized when a train approaches, the solenoid armature is 




U) 







(B) 
Fig. 322. — Locomotive types of crossing bells. (Railroad Supply Co.) 

drawn downward causing the hammer to strike the bell. Just as 
it is drawn down far enough to make the hammer strike, the current 
is broken by the snap-switch, and the hammer falls by gravity. 
When the armature reaches its normal position, it completes the 
circuit through the snap-switch and energizes the relay to ring 



HIGHWAY CROSSING SIGNALS 



305 



the bell again. The process is repeated 40 to 60 times a minute 
giving as many blows to the bell. This equipment can be used 
only with direct current. 

The locomotive bell may be operated also by a motor as shown 
in (B). By means of a train of gears, the motor drives a cam 
that raises and lowers a weight to which is attached the bell 
hammer. The weight simply serves to give regularity to the 
striking of the bell. The motor may operate on either direct 
or alternating current. 



w 




^ 



/lOVol tAC.Line a 



SS 



Wigwag Motor 
~ir\ 5' n Lamps 
C- /i.e. Crossinq Bell 
P - Non-lntGrlockinq Relou 
E- Track Battery 



Fig. 323.— 110- volt A.C. wigwag 



circuit. 
Co.) 



Double track. {Railroad Supply 



187. Highway Crossing Signal Circuits. — Figure 323 shows the 
wiring for operating the motor, lights and bell by 110-volt 
alternating current. The relays are of the neutral type controlled 
by simple track circuits. The approach of a train makes back 
contact with the relay armature and completes the circuit to 



f 




Fig. 324. — Low voltage signal circuit for double-track line. 



operate the wigwag and the bell. The wigwag is actuated by a 
motor connected to it through a train of gears. 

Figure 324 shows the wiring for operating highway crossing 
signals by low voltage on a double-track line. A bonded track 
section with ordinary track circuits is established for about a 
half mile on the approach side of each track. Insulated joints 

20 



306 



RAILWAY SIGNALING 



are maintained at each end of each section. Two ordinary 
relays would meet all of the requirements, but an interlocking 
relay with the interlocking device removed is sometimes more 
desirable, for it is equipped with better connections for such 
service and occupies less space. A train in either section, A or B, 
will shunt the relay for that section and cause the signal to 
operate as long as either of the blocks is occupied. As soon as the 
train moves out of the block, the relay becomes energized again 
and the signal resumes its normal position. A train backing up 
towards the crossing would not cause the signal to give any 
indication of such movement. 

In the case of single-track operation, the block on each side of 
the highway crossing must be bonded, and track circuits estab- 
lished, but an interlocking relay is required to prevent the sig- 



Jfe 



/I- Wigwag Motor 
B'^ '^ . Lamps 
C -Cross mg Bel/' , 
P- Inferlockmg Re/au 
B- Local Bafferu ^ 
F' Track dafferu 




& 



g 



^- 



SSIB 



Fig. 325. — Low voltage wigwag circuit. Single track. {Railroad Supply Co.) 



nal from giving a warning indication after the train has cleared 
the crossing. Figure 325 shows the wiring for a single-track 
road. 

188. Interlocking Relay. — Figure 326 illustrates the operation 
of one type of interlocking relay. Neither of the blocks is 
occupied and both track relays are energized. When a train 
enters from the left at A, relay K becomes deenergized and its 
armature drops away by gravity. The arm D strikes pawl F, 
tilting it slightly to the left, while finger E makes back contact 
with M, causing the signal to give the warning indication. 
As soon as the front of the train crosses the insulated joint B, 
the relay L becomes deenergized and its armature drops. It 
cannot make back contact, however, at iV, for the arm / falls 
into the notch / on the other side of pawl F. After the train 
has cleared the crossing the relay K becomes energized again and 



HIGHWAY CROSSING SIGNALS 



307 



the signal ceases to give its indication. The arm J is still held by 
the pawl F. As soon as the train has passed the insulated joint 
C, the relay L becomes energized and lifts its armature. 



JTRAIN[> A 



F=. . 


n II 1 . ^ 


UU^^ii 



F 

M N 

FIG. I 



rrn 



IJ^ 



]train|^ 




Jtrain [ X 




]train [ ^ 



' J i~ 



^f^^ 



jt"^'n| >: 



D H I J I y 

I II !T7 ~<^_ I II f 



l_| F LJ 

M N 

FIG.V 



Fig. 326. — Diagram showing operation of Union interlocking relay. 



Figure 327 represents a type of interlocking relay in which the 
interlocking arms form a part of the operating circuit. The 
diagram shows the operation of the relay as a train passes through 
the two track circuit sections. In (a), the track circuits AB and 
BC are unoccupied and the bell circuit is open. The train has 
entered track circuit AB, in (b), and has deenergized the magnet 



308 



RAILWAY SIGNALING 



L. The armature L-1 has fallen forward causing finger L-2 
to make contact with M, closing the circuit and ringing the bell. 
In (c), the train occupies both track circuits AB and BC. It has 
deenergized the relay R and the finger R-2 has fallen upon finger 
L-2. In (d), the train occupies track section BC, The relay L 



\ r , 



i4' 



Track Circuit A B and B C unoccupied. 
Bell Circuit Open. 



.:na 



r-^ 



\ZX.. 



m 



Fig. 1 



T^ 



1 IJ 



■t-r 



t-rdh 



Train has entered Track Circuit A 
B Relay Magnet L. De-energized 
Armature L-1 causes Contact 
Finger L-2 to make Contact with 
M Bel! Circuit Closed. 






— r 



Train in Track Circuit A B and B C 
(at crossing) Relay Magnet R 
De-energized Contact Finger R-2 
Resting on L-2 Eel! Circuit Closed 



i^G3 



G3- 




Train in Track Circuit B C Relay Magnet L Ener- 
gized Contact Finger R-2 resting on L-2 Bell Circuit 
Open. When Train passes out of Track Circuit B C 
all parts normal as in Fig. 1. 

Operation similar in either direction. 

Fig. 327.— Diagrams. a, b, c and d showing the operation of style "A" universal 
crossing bell relay. {Chicago Railway Signal and Supply Co.) 

has become energized again and its armature has lifted the finger 
L-2 clear of contact M. This action has opened the bell circuit 
and has caused the bell to stop ringing. 

189. Hoeschen Bell System. — Figure 328 represents a Style 
''A" selective magneto-generator for the Hoeschen system of 



HIGHWAY CROSSING SIGNALS 



309 



crossing signals. The motive power used to operate the bell is 
obtained from the natural spring of the rail, which is utilized by 
means of levers placed under the base of the rail. An illuminated 




Fig. 328. — Style "A" selective magneto-generator. Hoeschen system. 

sign that remains illuminated only while the bell is ringing may be 
used also to give additional warning. 

Figure 329 shows the generator with the cover removed. B 




Fig. 329. — Style "A" generator with cover removed. 

represents the armature at rest on the induction coils, C, C, 
which are fastened to the poles of a group of three permanent 
magnets, D, D; E represents the armature rocker tripping pin. 



310 



RAILWAY SIGNALING 



which rests on the upper ends of the two vertical rods F and G. 
These rods are supported on the ends of scale levers and S, 
which are termed ''operating" and ''shunt/' and are placed in a 
V-shaped position with their outer ends resting firmly against 




the under side of the rail. These levers being fulcrumed close 
to the rail multiply the depressions caused by a passing train. As 
the ratio of the lever arms is 1 to 12, a depression of }{q in. gives 
the inner end of levers and S an upward stroke of % in., which 
is sufficient to operate or shunt the generator as may be required. 



HIGHWA Y CROSSING SIGNALS 



311 



K, K represent the housings for spiral compression springs with 
plunger resting on scale levers and S so as to increase or decrease 
the tension of these levers. Two wires lead out from the induc- 
tion coils through a lightning arrester to wires W, W and thence 
to the bell. SS represent heavy springs used to protect the 
mechanism from excessive vibration caused by the passing trains. 

Figure 330 represents a dia- 

gram for single-track installation 
of this system. Levers and S 
are so arranged that the operat- 
ing lever is always depressed 
slightly in advance of the shunt 
lever as a car or train, moving 
towards the crossing, passes over 
the track opposite the generator. 
The depression of the operating 
lever forces the vertical rod G up- 
wards, thus imparting both an 
upward and inward motion to 
the armature rocker tripping 
pin E. This brings it in contact 
with the armature B with suffi- 
cient force to separate the arma- 
ture quickly from the poles of the 
induction coils C, C, thus gener- 
ating a momentary current of 
high voltage that is transmitted 
to the bell. As the car moves 
from the crossing, the shunt lever 
is depressed in advance of the 
operating lever. The depression 
of the shunt lever forces the rod 
F upwards, imparting both an 
upward and an outward motion 

to the tripping pin E. This allows the pin to pass the end of 
the armature, and the depression of the operating lever imme- 
diately afterwards has no actuating effect. 

Figure 331 shows the motor of the signal equipped for single- 
track operation with both time and automatic contact attach- 
ments. The motor consists of a simple gear movement of three 
wheels used in connection with three powerful motor springs. 




Fig. 331. — Details of Hoeschen bell 
mechanism. 



312 



RAILWAY SIGNALING 



The selective generators are connected in series with the releasing 
magnets, M, M, by separate metallic circuits running each way 
from the crossing, as shown in Fig. 330. Each pair of releasing 
magnets is equipped with a pointed armature iV, iV, and both 
these armatures engage the releasing clutch lever L. This lever L 
engages the releasing lever RL and holds it as shown when the 
motor is not in motion. When either of the releasing magnets 




Fig. 332. — Hoeschen crossing signal. 

is energized by the operation of the selective generator, its 
armature N lifts the clutch lever L, thus releasing the motor 
through the lever RL. As the escapement wheel turns from 
right to left, it imparts a rocking motion to the rocker RR, which 
is connected direct by rod RO to a pendulum bell hammer that 
strikes at regular intervals the inner side of a locomotive type 
of bell, shown in Fig. 332. 

The motor is provided with both an automatic and time 



HIGHWAY CROSSING SIGNALS 313 

stopping device. The time stopping arrangement operates as 
follows: When a motor is released and the escapement wheel 
starts to turn from right to left, it exerts a slight pressure on a 
counterweight that is fastened to the inner end of the RL lever 
shaft directly above the escapement wheel. This movement 
forces lever RL to move slightly to the left, where it is locked by 
the latch lever V; and it remains in this position until released 
by the sliding sawtooth bar XX. As each revolution of the 
escapement wheel raises this bar one notch or tooth by means of 
the small stud on the hub of the wheel, it raises the lever F, and 
allows lever RL to swing back to normal by force of the counter- 
weight, thus stopping the motor. 

The automatic cut-out or stopping mechanism is operated 
simultaneously with the winding of the motor by a passing train. 
The slight depression of the rail of }i2 or }y{Q in., caused by 
a passing train, imparts a rocking or reciprocating movement to 
the bell crank lever resting against the under side of the rail. 
This motion is transmitted by a connecting rod through the 
rocker plate RP to the two winding arms WA which are provided 
with ratchet dogs on the inner sides that actuate the ratchet 
wheel and wind the springs. This operation imparts the recip- 
rocating motion of the rod AA fastened to the right winding 
arm WA and connected by friction clutch lever FC to latch 
lever V, thus releasing the RL lever and allowing it to move 
back to its normal position, thereby locking the escapement 
crank and stopping the motor. 

A small dial with a pointer is shown on the face of the motor. 
This indicates to the signal maintainer the amount of potential 
energy stored up ready for servi'ce. The motor is always nearly 
or entirely wound and provision is made to prevent overwinding. 
When fully wound it will deliver about 20,000 strokes on the bell 
and will run continuously for an hour and forty minutes. 

Figure 333 shows a cross-sectional view of the Style ''S" 
magneto-generator, a newer type designed to meet the demands 
of ''safety first." The mechanism is constructed to operate by 
the depression of the rail under the wheels of a passing train in 
practically the same manner as the Style ''A'' generator. The 
operation of the generator is made selective, or directional, 
by the use of a selector instrument designed along the same gen- 
eral lines as the generator. It is installed from 4 to 6 ft. from 
the generator in the direction from which no operation is desired, 



314 



RAILWAY SIGNALING 




AAAVV\A 



HIGHWAY CROSSING SIGNALS 



315 



the weight, section and stiffness of the rail determining the 
spacing between generator and selector. The instrument con- 
sists of a simple spring switch that stands normally open which is 
connected in multiple to the two line wires running from the 
generator to the bell. A car or train going from the bell or signal 
passes over the selector, causing the switch to close by means 
of a plunger and scale lever arranged as in the generator. The 
selector operates a fraction of a second 
before the generator, and the current gen- 
erated by the operation of the magneto is 
shunted out from the line by the closed 
switch on the selector. For traffic ap- 
proaching the crossing the selector remains 
unaffected, with its shunt switch open, until 
the generator has operated, thus permitting 
a closed circuit from the generator to the 
bell. 

190. AGA Highway Danger Signals. — 
Figure 334 illustrates an AGA Highway 
Danger Signal. The round lamp box at 
the top is 30 in. in diameter with trans- 
parent letters around the face of it and a 
flasher in the center behind the S%-m. 
red spread-light lens. The day and night 
indications are both given by an acetylene 
light flashing through the red lens and the 
transparent letters. The center of the 
lens is 6j^ ft. above the concrete foot- 
ing. The entire sign is made of cast 
iron. The lamp-box rests on a housing, 
which contains the gas cylinder, high- and 
low-pressure equipment, and the electro-gas valve when the 
signal is used as a railroad crossing sign. 

The cylinder is filled with gas to a pressure of 150 lb. per 
square inch at a temperature of 60°F. From the cylinder, the 
gas flows through a regulator that reduces the pressure to less 
than 1 lb. a square inch, and then it passes on to the flasher 
shown in Fig. 335. After the gas passes through the pipe B of 
the flasher into the small chamber C, a part of it goes to feed the 
pilot burner D, and the remainder passes through opening E 
into the gas chamber F. After enough has accumulated in this 




Fig. 334.— AGA high- 
way danger signal. 



316 



RAILWAY SIGNALING 



chamber, the pressure forces the diaphragm G downward puUing 
with it the lever H and thereby unseating it at *S. The gas 
escapes through the passage / to the burner K, and the pilot D 
ignites it to produce the flash. As the passage S is much larger 
than the opening E, the gas escapes faster than it enters; and as 
soon as the pressure drops sufficiently, the diaphragm and lever 
return to their original position. The end of lever H is magnet- 
ized to eliminate any lag in opening and closing the passageway 
S. The frequency of the flash is regulated by the lever L. 

When used as a highway approach signal, where it stands at 
the side of the highway, possibly 300 ft. from the crossing, the 




Fig. 335. — AGA signal flasher. 



size of the burner is ^q it. and gives a flash during one-tenth of 
the entire frequency cycle. The number of flashes can be what- 
ever desired, but the usual practice is 60 a minute. In 24 hours 
of continuous operation the signal consumes 0.8 cu. ft. of gas. 
When placed on the right-of-way as a grade crossing signal, 
the flow of gas to the flasher is controlled by an electro-gas valve 
operated in connection with track circuits, so that the signal 
flashes only while a train immediately approaches the crossing. 
The size of the burner is % ft. and gives a flash during one-fourth 
of the frequency cycle. Outside of the gas consumed by the 
pilot, which is 0.3 cu. ft. in 24 hours, the total amount used per 
day varies directly with the amount of train service ; but with 30 
trains each way a day, allowing three minutes for each movement. 



HIGHWAY CROSSING SIGNALS 



317 



the gas consumption will be only 0.6 cu. ft. per 24 hours including 
that burned by the pilot. The red light can be seen in dayhght 
for a distance of 600 ft. 

The AGA Company has another signal, Style ''B/' which 
operates in connection with track circuits, that has two lenses 
the upper one of which gives continuous green flashes, except, 






1 ' 






i ^ 


^ 


— ^ 


Ij. 






'# 




V 

s 


) 


1 

















'•i 


^ ,^. - 




A 


/ 


\ 



/ !^ 20 SQ >1 \ 



f 



Fig. 336. — AGA two-color highway danger signal. 

while a train approaches the crossing, when they are red as before. 
This type of signal is illustrated by Fig. 336. When a train 
enters the hghting track circuit the electro-gas valve closes the 
outlet to the burner in the top lamp and opens the inlet to the 
burner with the red lens giving a series of red flashes. As soon 
as the train passes out of the block, however, the flashes become 
green again. 



APPENDIX A 

RULES 

GOVERNING THE CONSTRUCTION, MAINTENANCE AND OPERA- 
TION OF INTERLOCKING PLANTS^ 

PRELIMINARY REQUIREMENTS 

Section 1 — Indications and Aspects. — (a) As far as practicable, a uniform 
system of indication and aspects must be used for each operating division. 
When requested every railroad company operating in this state shall submit 
plans to the Commission showing the system of indications and aspects in 
use, or which it proposes to use for fixed signaling for each operating division. 

(6) If changes are made by any railroad company in its system of signal 
indications and aspects on any operating division in this state subsequent 
to the filing of plans, it shall notify the Commission accordingly. 

Sec. 2 — Plans to be Submitted. — (a) Prior to the construction, reconstruc- 
tion or rehabilitation of any interlocking plant, there shall be filed with the 
Commission as a basis for approval, the following plans : 

(6) A station map or other plat, drawn to scale, showing all tracks, bridges, 
buildings, water tanks, and other physical surroundings located on the right 
of way of each company. 

(c) Profiles showing the grade of each railroad company's main tracks for a 
distance of not less than two (2) miles in each direction from the crossing or 
junction. 

(d) A track plan in duplicate (and as many more as the roads desire 
approved) showing the location of all interlocking units, the tower and its 
general dimensions, and any other appurtenances necessary to show a 
complete layout of the proposed interlocking plant. When not expedient to 
locate accurately all physical characteristics by figures, they should be 
established by scaled distances within the interlocking limits hereinafter 
specified. 

(e) When merely changes and additions are involved, no station maps or 
profiles need be filed with the track plans except when requested by the 
Commission. 

(/) All plans filed with the Commission under this and other sections must 
be of light weight paper when in the form of blue prints. 

Sec. 3 — Symbols. — In the preparation of plans, the symbols approved by 
the Railway Signal Association shall be used to indicate switches, derails, 
signals and other essential parts of the interlocking plant. 

Sec. 4 — Limits of Interlocking Plants. — The interlocking limits are defined 
by the home or dwarf signals situated on any specified track and located 
farthest from the point to be protected. Any appliances operated in 

1 Prepared jointly by the engineers of the Railroad Commission of Wisconsin, the 
Railroad & Warehouse Commission of Illinois, the Railroad & Warehouse Commission of 
Minnesota, and the Public Service Commission of Indiana, and adopted by their respec- 
tive commissions. 

318 



APPENDIX 319 

conjunction with the interlocking plant, and situated beyond the limits 
herein designated, are considered as auxiliaries. 

Sec. 5 — Approval of Plans. — (a) When possible, the railway companies 
concerned should agree on the plans before submitting them to the Com- 
mission. 

(h) If the preliminary plans are satisfactory, or if in the judgment of the 
Commission modifications are necessary, the plans will be approved 
accordingly. Of the plans so approved, one copy will be retained by the 
Commission, and the duplicate returned to the petitioning company. 

(c) The approval herein described will stand for a period of one year. If 
the work is not commenced within that period, a new approval must be 
obtained. 

Sec. 6 — Physical Changes, Reconstructions and Rehabilitation. — No 
interlocking plant shall be reconstructed or rehabilitated, nor shall any 
change be made in the locking or in the location of any unit, until plans have 
first been submitted to and approved by the Commision. 

Sec. 7 — Conditional Service. — (a) Upon the completion of any work on 
interlocking plants which involves changes in the locking, the units must be 
connected and adjusted, the plant placed in conditional service for not less 
than twenty-four (24) hours, and remain so until relieved by order of the 
Commission. 

(6) When minor changes are made in locking under plans previously 
approved by the Commission, it will not be necessar}^ to place the plant 
in conditional service prior to the time it is ready for inspection; and in 
cases when permission is received from the Commission in advance, the 
plant may be placed in full operation, if the Commission is unable to inspect 
it within twenty-four (24) hours after it is ready for inspection. 

(c) Conditional service is hereby interpreted to mean that all units and 
other apparatus involved be connected and operated from the interlocking 
machine in the tower. All trains shall come to a stop at the governing home 
or dwarf signal regardless of its position and that such signal shall not be 
operated to give a proceed indication until after the train has made the 
prescribed stop. 

Sec. 8 — Petition for Inspection. — (a) Prior to or accompanying the 
petition for inspection of completed interlocking plants, the following de- 
tailed plans will be required : 

(6) A track plan similar to the one referred to in section 2, showing all 
tracks and interlocking units as actually constructed, the terminal ends of 
each track to be numbered or lettered for use in connection with the manipu- 
lation sheet. A locking sheet and dog chart showing the arrangement of 
locking in the machine as installed; wiring plans showing in detail all circuits 
used in connection with the plant; a manipulation sheet with or without 
track diagrams as required by the Commission, showing in tabulated form 
the numbers of all levers necessary to be manipulated for any given route 
designated on the track plan. 

(c) A suitable framed manipulation chart and track diagram shall be 
properly placed in the interlocking tower. The terminal ends of each track 
on this chart shall be numbered or lettered to correspond with the track 
plans above mentioned. 



320 RAILWAY SIGNALING 

(d) The petition for inspection of any interlocking plant, when possible, 
shall give three (3) days' notice in advance of the time when the plant will 
be ready for inspection. Upon receipt of such notice, the Commission will 
endeavor to have the plant inspected within three (3) days after receiving 
such advice. If the Commission is not able to make the inspection within 
the time specified, it will authorize the railroad company in charge to place 
the plant in full operation, subject to future inspection. 

(e) If upon the inspection of any interlocking plant by the Commission, it 
is found to be installed in accordance with the approved plans, a temporary 
permit will be issued to the railroad company in charge, pending the issuance 
of formal permits. 

REQUISITES OF INSTALLATION 

Sec. 9 — Type of Signals. — (a) Except when approved by the Commission, 
all interlocking signals must be of the semaphore type. The apparatus 
connected with the operation of these signals must be so constructed that the 
failure of any part directly controlling the signal will cause it to display its 
least favorable indication. 

(h) Semaphore arms must display indications to the right of the signal 
post, except where the physical conditions on a road require the display of 
signal indications to the left. 

Sec. 10 — Location of Signals. — (a) All fixed signals must be located 
either over or upon the right and next to the track over which train move- 
ments are governed, except on roads operating trains with the current of 
traffic to the left, or where physical conditions require placing the signals 
to the left of the track. 

(6) Bracket post signals may be used on roads operating trains over two 
(2) or more tracks in the same direction, when such practice is uniform for 
any specified operating division, or where local conditions require their use. 

Sec. 11 — Locking of Signals. — The locking between the levers of the in- 
terlocking machine must be arranged so that a home or dwarf signal cannot 
be cleared for any given route unless all switches, derails, movable point 
frogs and other units in the route are in proper position and locked. 

Sec. 12 — Home Signals. — (a) When required by the Commission, all 
home signals must be equipped with not less than two arms. Unless 
operated by power all home signals in mechanical plants must be pipe con- 
nected except when otherwise approved by the Commission. 

(6) When used in connection with automatic train stopping devices, the 
home signal may be located immediately opposite the means for controlling 
the apparatus of the train stopping device. 

(c) When used in connection with derails and other units the home signal 
must be located as far in advance of such units as is necessary to secure full 
protection, but in no case shall it be less than five (5) feet in advance of such 
units. 

(d) When home signals are semi-automatic, or form a part of an auto- 
matic block signal system, calling-on-arms or some other means may be 
used for advancing trains. 

(e) All high speed signals located in automatic block signal territory 
shall be semi-automatic and form a part of the block signal system. 



APPENDIX 321 

Sec. 13 — Dwarf Signals. — Dwarf signals indicate slow speed movements 
and may be used to govern train movements on all tracks other than 
main tracks, except as hereinafter specified; on main tracks to govern train 
movements against current of traffic, and when approved by the Commis- 
sion as intervening signals to facilitate switching movements. When used 
they must be located and connected in the same manner as home signals. 

Sec. 14 — Advance Signals. — Advance signals may be used when neces- 
sary, and must be installed in the same manner as home signals. 

Sec. 15 — Distant Signals. — (a) On level and ascending grades, distant 
signals shall be located not less than two thousand five hundred (2,500) feet 
in advance of their respective home signals. On descending grades the 
minimum distance of two thousand five hundred (2,500) feet shall be in- 
creased at the rate of one hundred (100) feet for each one-tenth (1-lOth) of 
one per cent of gradient. 

(b) Where conditions justify, the location and character of distant signals 
or the method of operation may be varied or the signals be omitted, depend- 
ing upon the conditions surrounding each particular case. 

(c) Except as hereinafter provided, all high speed tracks must be equipped 
with power-operated distant signals having electric locks or other suitable 
apparatus to prevent changing of the route until such signals have indicated 
their normal position. 

(d) When required by the Commission, distant signals shall be so arranged 
as automatically to indicate stop when the track between the home and 
distant signals is occupied, or when any intervening switch is not in its 
normal position. 

Sec. 16 — Switches. — All switches, derails, movable point frogs and other 
units within the interlocking limits hereinbefore defined must be incorpor- 
ated in the plant. 

Sec. 17 — Derails on Steam Roads. — (a) Main Tracks: On level grades 
facing derails must be located not less than five hundred (500) feet from a 
drawbridge or the fouling point of a crossing or juncftion. On descending 
grades facing derails must be located to give practically the same measure 
of protection as for level grades, and the minimum distance of five hundred 
(500) feet must be increased at the rate of ten (10) feet for each one-tenth 
(1-lOth) of one per cent gradient. On ascending grades the minimum 
distance of five hundred (500) feet may be reduced at the rate of ten (10) 
feet for each one-tenth of one per cent gradient; but in no case shall such 
derails be located less than four hundred (400) feet from a drawbridge or 
the fouling point of a crossing or junction. 

(6) Pocket Derails: Where such are used they shall be located so as to 
derail the first pair of wheels on the ties at a point not less than fifty (50) 
feet from the fouling point of a crossing or junction. 

(c) Back-up Derails: These shall be placed not less than two hundred 
fifty (250) feet from a drawbridge or the fouling point of a crossing or 
junction. 

(d) Secondary Tracks : All tracks other than main tracks shall be termed 
secondary tracks. On such tracks derails shall be placed not less than two 
hundred (200) feet from a drawbridge or from the fouling point of a crossing; 
and not less than fifty (50) feet from the fouling point of a junction, 

21 



322 RAILWAY SIGNALING 

(e) The fouling point is where two trains moving toward a common center 
would come in contact. 

(/) Where conditions justify, the location of derails may be varied or they 
may be omitted, when approved by the Commission. 

Sec. 18 — Derails on Electric Roads. — The location of derails on electric 
roads shall be determined in the same manner as for steam roads. In 
placing derails in the tracks of such roads, consideration will be given to 
speed and character of traffic. 

Sec. 19 — Type of Derails. — Derails must be of an approved pattern, 
suitable for the purposes intended and so placed with reference to curvature, 
bridges and other tracks as to secure a maximum of efficiency and safety. 

Sec. 20 — Guard Rails. — Where physical conditions require their use, 
guard rails shall be installed in connection with derails. When used, they 
shall be placed between the track rails, parallel to and not less than ten (10) 
inches distant in the clear therefrom, and must be of sufficient height, length 
and strength, and be properly secured to the track ties. 

Sec. 21 — Automatic Train Control. — Automatic train stopping devices 
w^hich are a part of a system of automatic train control approved by the 
Commission, may be used in lieu of derails. In such devices, the means for 
automatically applying the train brakes shall be located a sufficient distance 
in advance of the fouling point as to insure a safe braking distance. 

Sec. 22 — Locks. — (a) In mechanical plants all facing switches, split point 
derails in main tracks and all slip switches and movable point frogs, must be 
locked with facing point locks. All other derails, switches and other units 
must be locked either with facing point locks or with switch and lock 
movements. 

(6) In plants equipped with mechanical signals, all derails must be pro- 
vided with bolt locks; also all switches, movable point frogs and other units, 
where conditions require them. 

(c) In power plants, the arrangement must be such that the signals 
operating in connection with derails, facing point switches and other units 
cannot be operated unless these units are in proper position. 

Sec. 23 — Detector Bars. — (a) Unless otherwise provided, all derails, 
switches, movable point frogs and other units shall be equipped with detector 
bars of approved design not less than fifty-three (53) feet in length, or longer 
if required. 

(b) Except as hereinafter provided, all crossings shall be equipped with 
detector bars of suitable length, so interlocked as to insure a clear crossing 
before an opposing route can be set up or a proceed signal given. 

(c) Crossing detector bars will not be required where electric locking is 
installed ; nor at outlying crossings of simple character where no switching 
is performed, when the plant is equipped with time locks. 

Sec. 24 — Time Locks. — Unless equipped with electric locking, time locks 
must be installed to prevent the changing of high speed routes, until after 
the home signal has displayed the stop indication a predetermined time. 

Sec. 25 — Electric Locking. — Electric locking may be provided in place 
of time locks and crossing bars. When used, the circuits must be arranged 
so as to prevent the changing of a route until the train has passed through 
the interlocking limits or through a predetermined part of the plant. 



APPENDIX 323 

Sec. 26 — Detector Circuits. — When a railway company is equipped with 
sufficient maintenance forces for properly maintaining electric detector 
circuits, such circuits may be used in place of mechanical detector bars. 

Sec. 27 — Machines. — (a) All mechanical interlocking machines shall be 
equipped with locking of the preliminary type. 

(6) All power interlocking machines shall have the locking so arranged 
as to be effective before the operating conditions of any circuit directly 
controlling a unit can be changed. Suitable indicating and locking ap- 
paratus shall be provided to prevent the placing of a lever in complete normal 
or reverse position until the unit controlled has completed the intended 
operation, except that signals shall indicate the normal position only. 

Sec. 28 — Locking of Levers. — (a) The locking must be so arranged that 
conflicting routes cannot be given at any stage in the setting up of a route, 
nor a proceed indication given until all switches, derails, movable point 
frogs, facing point locks and other units in the route affected are in proper 
position. 

(6) When a separate lever is used to operate distant signals the locking 
between the home and distant signals shall be so arranged as to prevent the 
distant signals from giving the proceed indication until the home signals 
operating in connection with such distant signals are in the proceed position. 

Sec. 29 — Locks and Seals. — (a) All interlocking machines must, when 
practicable, be provided with means for locking or sealing the mechanical 
locking and indication apparatus in such a manner as to prevent access to 
any except authorized employes. 

(6) All power interlocking cabinets, time locks, time releases, emergency 
switches, indicator and relay cases must be provided with suitable covers 
and fastenings and be properly sealed or locked, and must not be opened by 
any but authorized employes. 

Sec. 30 — Cross Protection. — (a) As far as practicable, cross protection 
apparatus must be provided in connection with electric interlocking plants 
to prevent the operation of any unit by cross or grounds. 

(6) Low voltage circuits, as far as practicable, must be designed to prevent 
the operation of apparatus by cross or grounds. 

Sec. 31 — Annunciators. — When operating conditions require annun- 
ciators, they shall be installed. 

Sec. 32 — Signal Towers. — (c) Signal towers shall be so placed and be of 
such height and size as to best serve the purpose for which they are intended. 

(5) The use of interlocking towers for purposes other than interlocking, 
dispatching and block work is undesirable. 

(c) If work other than interlocking is carried on in the tower, a suitable 
partition or railing must be provided to prevent outsiders from having 
access to interlocking apparatus, and interfering with the duties of the opera- 
tor or towerman. 

Sec. 33 — Tower Lights. — The tower lights must be screened off so that 
they cannot be mistaken for signals exhibited to control train movements. 

Sec. 34 — Material and Workmanship. — Material and workmanship must 
be first-class throughout. When complete, the interlocking plant must be 
in every way suitable and sufficient for the purposes intended. 



324 RAILWAY SIGNALING 

MAINTENANCE AND OPERATION 

Sec. 35 — Maintenance and Operation. — (a) Interlocking plants must at all 
times be properly maintained and efficiently operated. Any rules or regula- 
tions that the railway companies may have adopted for the guidance of 
employes in operating and maintaining interlocking plants must be appro- 
priately framed and conveniently placed in interlocking towers. 

(h) When an interlocking plant is taken out of service the Commission 
must be notified immediately. Under such circumstances train movements 
must not be governed by interlocking signals but by the usual precautions 
prescribed by statute governing train movements over and across railway 
grade crossings, junctions and drawbridges. 

Sec. 36 — Interlocking Reports. — Reports for each interlocking plant shall 
be filed with the Commission by each railroad company concerned, which 
reports must be filed in manner and form prescribed by the Commission. 






APPENDIX B 

PART I 
SIGNAL ASPECTS 

The following memorandum on the essentials of signaling, 
incorporated in the report of the Committee on Transportation of 
the American Railway Association, May, 1911, is copied from 
the Manual of the Railway Signal Association: 

"The reports of various Committees of the Railway Signal Associa- 
tion and of the American Railway Engineering Association on the subject 
of signaUng have been submitted to this Committee, with the request 
that the essentials of signaling be outUned or defined for the future guidance 
of their Committees. 

The subject has been carefully analyzed and considered. There are 
three signals that are essential in operation and therefore fundamental, viz : 

(1) Stop. 

(3) Proceed with caution. 

(3) Proceed. 

The fundamental, "proceed with caution," may be used with the same 
aspect to govern any cautionary movement; for example, when: 

(a) Next signal is "stop." 

(b) Next signal is "proceed at low speed." 

(c) Next signal is "proceed at medium speed." 

(d) A train is in the block. 

(e) There may be an obstruction ahead. 

There are two additional indications which may be used where movements 
are to be made at a restricted speed, viz: 

(4) Proceed at low speed. 

(5) Proceed at medium speed. 

Where automatic block system rules are in effect, a special mark of 
some distinctive character should be applied at the stop signal. 
The Committee therefore recommends: 

Signal Fundamentals 

(1) Stop. 

(2) Proceed with caution. 

(3) Proceed. 

Supplementary Indications to be Used Where Required 

(4) Proceed at low speed. 

(5) Proceed at medium speed. 

Stop signals operated under automatic block system rules should be 
designated by some distinctive mark to be determined by each road in 
accordance with local requirements." 

325 



326 



RAILWAY SIGNALING 
Recommendations of Committee I 



Your Committee submits for approval the following two schemes of 
signaling in conformity with the recommendations of the Committee on 
Transportation. 

Scheme No. 1 



A Sfop 

2. Proceed with Caution 

3. Proceed 



r 



FUNDAMENTALS 

^ J] 



As means of designating stop signals operated under automatic block 
system rules, the following are suggested : 

1. The use of a number plate; or 

2. The use of a red marker light below and to the left of the active light; or 

3. The use of a pointed blade, the blades of other signals giving the stop 
indication having square ends ; or 

4. A combination of these distinguishing features. 



Scheme No. 2 



FimAMFNTAL^ SUPPLEMENTARY 
FUNDAMENTALS ff^p/cATIONS 



f.'3hp 



2r Proceed 
wifh Caution 



3.- Proceed 




4- Proceed a f 
Low Speed 



5- Proceed at 
Medium Speed 






As means of designating stop signals operated under automatic block sys- 
tem rules, the following are suggested : 

1. The use of a number plate; or 

2. The use of a red marker light below and to the left of the active light; or 

3. The use of a pointed blade, the blades of other signals giving the stop 
indication having square ends; or 

4. A combination of these distinguishing features. 

Having in view the practice of indicating diverging routes by several arms 
on the same mast, the Committee submits for approval the following to 
establish uniformity in this practice: 



APPENDIX 



327 



Scheme No. 3 



/. Si-op 



2 Pracsecpl with CauHon 



3 Prc?ceed 



\<? 



V? V? 



H or 

^ XI |II 

Z2 



4 Proceed wif-h Cau+ion on ihe Low-Speed Route 



^or -x^or l(^ 



5. Proceed on ihe L ow Speed Foufe 



ID 



6. Proceed w'lHi CauHon on Medium-speed Roufs 



^ 



7 Proceed on the Medium-Speed Route 



n 



v> \o 



8. Reduce to Medium Speed 



H 



H 



328 RAILWAY SIGNALING 

As means of designating stop signals operated under automatic block 
system rules, the following are suggested : 

1. The use of a number plate; or 

2. The use of a red marker hght below and to the left of the active light; 
or 

3. The use of a pointed blade, the blades of other signals giving the stop 
indication having square ends; or 

4. A combination of these distinguishing features. 

The above three schemes are submitted, after an earnest effort to carry out 
the Committee's instructions to submit a uniform scheme of signaling, with 
the idea that each scheme is complete in itself. 



PART II 
SYMBOLS 

The following plates, 1-13, are symbols recommended 

by the Railway Signal Association for use 

in railway signal practice. 



330 



RAILWAY SIGNALING 



Operating. 



Mechanicai 



irtcs 



NOM- Automatic. 



Power 



Slotted. 

(mech.) 



Semi-Automatic. 



Stick. 



t3 



Non-Stick 



to 



Automatic 
(power) 



til 



SPECIAt 

RCrCRENCC 
TONOTO 



tS3 



Two 
Position 

SiGNAUNG, 



2- Position. 
0to60-0to10 
0to75'0to9O 



y...^ 

;..-.j 



R 



A2 



H 



n 



A'5 



B 



A7 



2-P05ITI0H. 

OtoSO 



I-Lj 



162 



I B3 



B4 



B5 



B7 



Three 
Position 
S1GNIU.1N6. 



2- Position. 
Oto4S 



t^ 



P. 



^. 



^. 



C5 



1^ 
C7 



2- Position. 
45 TO 90 



4^' 



ft 



\t 



re 



^ 



3- Position. 
Oto45to90 



f^ 



fi 



E3 



f?. 



33 



E5 



NOTE: Arms should always be shown in normal position. 

Speciau - 3 Position Non-Automatic , to 45 . 
E24 Semi -Automatic Stick, 45 to 90. 

Special** 3 position Non- Automatic, Oto45. 

Semi -Automatic Non- Stick , 45 to 90 . 



■ I Absolute Stop Signal. j < Distant Signal. 

I I 

! > Permissive Stop Signal. { C Train Order Signal, 



Ends of blades in symbols are to be of the actual forms used by the 
road concerned. If not specified the above forms will be used on plans. 



y 



Fixed Arm. 



t**"j Upper Quadrant Signal. J 

«""* ^2 

i^l'lj '•^™ 9«aorant 5i6NAL. 

}" 

hl"J VERTIDAL 

I'D 




Marker Lights. Diagrams of Proportions for mak- 
Stoggered I ^^ symbols for signal blades . 



O! 



Plate I. 



APPENDIX 



331 



Ground 
Mast. 



tu 



HK 



Ground Mast with 
Bracket Attachment. 






n 



Offsct 
Bracket Post. 



I . j — -. 



T 

Bracket 
Post. 



"t 



Suspended 
Mast. 



Ring enclosed 
characteristics 

j_ MEAN U6HT SI6NA1 

ONLY. 



? 



Smash Signal 



Pot Signal. 



Home 
Proceed , 



Disc Signals. 

(i) @ @ (g 



home Distant Distant Double 

Stop. Proceed. Caution. Functioned. 



Present Signal to be Removed. 



y 



r 



Present Signal to Remain. 



Relation of the Signal to the Track and the Direction of Traffic 
Jl_ r.— H 



"^ Right Hand Locations. 



Right Hand Signal. 



Left Hand Signal. 



Left Hand Locatwns. 



n 



Right Hand Signal 



u 



left Hand Signal. 



Plate II. 



332 



RAILWAY SIGNALING 



Insulating Rail Joints. 

— "1 — 



Track Circuits in 
Both Directions. 



Track Circuit on Left, 
None on Right. 



Track Circuit on Right, 
None on Left. 



I 1 

Station. 



Signal 



^ ""lienor' ^^^ S^*Ti0N . 



^m Traffic Direction 
Signal Substation . Crossing Gate . 

Bridges. 



^n:^ 



Signal Bridge. Girder. Truss. Trestle. 

NOTE: State whether Deck, Half-through or Through Bridge. 



Lift Span . Bascule, Double Leaf. Bascule, Single Leaf. Draw Span . 



Highway Crossings. 



^LZ. 



J / 



^f i 




Street AND PuBuc Private Road Road Crossing Road Crossing Road Crossing 

Road Crossings. Crossing. at Grade. Undergrade. Overhead. 

D... ..«w T.«.«»» NOTE- Specify Steam or Electric where Electric 
nAILWAY I RACKS. Tracks Cross or Join Steam Tracks. 



RED. 



COU» OTHER THAN RED 8R 



Railwav Track or Old Track to be 
Old Track to Remain . Taken Up. 



Proposed 
Tracks 



BUCK W1TX INITIALS OF NOAD. 

Proposed (futvre) Foreign 
Tracks. Tracks. 



TuNNa. 

T X 







d] 



Track Instrument. Torpedo Machine. Impedance Bond. 
O ' 



>iw.T 



yjuu^ju 



Mile Post. Mail Crane. Water Tank. Water Column. Track Pan 

-4- _4_^-^^-_4_ _^ 



-^ 



-^ 



Non-Automatic. 



Slotted. 



^ 



Stop. 



Clear. 



Semi-Automatic. Automatic. 



Mechanical. . Power. 



OO Insulated 

Power Switch Machine. Switch Rod 



^ <^^y 



Turnout and 
Switch Stand. 



5 



Electric Switch Lock. 



Plate III. 



APPENDIX 



333 



Relay Box 



S 



E 



Junction Box 



Terminal Box Lightning Arrester 
Box 



D 



®-' 



CAPACITY 1-2 I 



RELAY BOX CAPACtTY- 



Take or Leave BATTEfrr 

SUXNG INDICATW ChUTE 



RELAY Box AND POST 



BATTERY CHUTE CAPACIT 




BATTERY ChUTE, RELAY 

Box AND Post Combined 



;^ 



Switch Box Location 



? 



NOTE : Type of indicator 
to be covered by 
general note 



Switch Indicator 



Switch Indicator 
and Switch Box 



I 



00 



i 



00 



Cable Post With One With Two With Relay With Relay With Relay 



Only 



Indicator Indicators 



Bahery Shelters 

MSj Above Surface 



a 



Half Above Surface 



1^5 J Below Surface 

(FIGURES indicate CAPACITY) 



Box Box and One Box and Two 

Indicator Indicators 



DC 



6 Ife b ^^^ 

c. 



Audible Visible Buzzer 

Highway Crossing Signals 



t-H 



■¥ 



m< 



B 



Track Battery 



Plate IV. 



334 



RAILWAY SIGNALING 



iNTmocKEo Switches and Derails 

^^y^y Siii6LE Switch ^^y^y 



StT FOR Turn-out 




Z 



'HfREE-WAY Switch 

2 



Set for Straight Track 



Set for Left Turn-out 




'\ 




z. 



^ 



Set for Straight Track Set for Right Turn-out 



Left hand DERAILS Right hand 

(OERAlLiyP) (N0N-0ERAIU{«) (derailing) (N0N-0ERAIUN5) 




Lifting Block 

NOTE Non-interlocked switches am) derails to be shovvn same as above except shading in triangles omitteo 
Where hano-thrown switches are pipe-odnnecteo to others, at least one switch or derail 
(the one farthest from point of operatwh) should have the letter 'p' placed beside it. 






.B;L-::U 



RL. 



ERL 



S.LM,, 



Detector Bar 



Bolt Locked Switch Plunger Locked Facing Point Lock Switch and Lock 



-S 



Oil ENaosED Pipe Line 



— C-V ^ 

Oil ENaosED Wire Line 



Switch 
Compensator 



Bolt Locks 



Movement 

Cranks 



Pipe Adjusting Screw 



Arrow Indicates Direction 
OF Movement of Pipe Line- 
Normal to Reverse 



I-Way 



Wire Aoousting Screw 



2-Way 



3-Way 



2-v;ay 



t 




3-Way 



track 



I^^ IffTERLOCKINe OR BLOCK STATION fS^!?! 

I r * N Showhs reumvE posmow of station, operctor and track v—~'^ 

Operator Facing Track Operator with Back to Track 

NOTE: UNLESS otherwise speofied on plan it will be assumed that where an interlocked 

SI6NAL is shown CLEAR OR A DERAIL SHOWN IN N0N-DERAIUN6 POSITION THE CON- 
TROLLING LEVER IS REVERSED, AND THAT Aa OTHER LEVERS ARE NORMAL. 



Plate V. 



APPENDIX 



335 



INTERLOCKED SWITCHES, DERAILS, ETC . 



9^. ^ 










^^ 3 -\ 


^^■^.^b 




^\^^ 


^^"^^ r*\ 


'"^P^ 


F^^ 


"<>.^^ 


.^v^ 2<;^2 


m.rfSvL 




^>^ 1 




^ 



Double Line Plan 




Single Line Plan 
EXPLANATION 




1 - Simple Turn-out 

2 - Simple Cross-over 
3- Derail -Single Point 
4- Single Slip Switch 



5 - Double Slip Switch 
6 -Movable Point Crossing Fros (M.P.F.) 
7-5IN6LE Slip Switch with M.P.F. 
8 -Double Slip Switch with M.P.F. 
9 - Rigid Crossing Frog 



Rocking Shaft Lead-out 



^ \ 



O WHEEL 



2 -WAY CRANK 
1-WAYCRANir<r 



12 3 4 6 7 8 9 

Crank Lead-out 



□ 



'2- WAY CRANKS 



vertical cranks 



Deflecting Bar Lead-out 

©^ ^-^ 



r\ 



HORIZONTAL DEFLECTING BARS 




/ / \ \ 

12 3 6 7 8 

VERTICAL DEFLECTING BARS 



Plate VI. 



336 RAILWAY SIGNALING 



Relays, Indicators and Locks. 

Elemihts of Symbols •pr 

TO BC COMBINED AS Ul ^ . C . ELECTRO MAGNET. 

NECESSARY. -LL 

^ A . C . Electro Magnet . 
i^.i i.-i Coil Energized OR Dc-ENERGizEO. 

1 . _Ij Neutral Front Contact - Closed or Open . 

T — r 

Neutral Back Contact - Closed or Open . 

Polarized Armature - With Conti^cts. 









3 -Position Armature -With Contacts. 



j..iz HIGH Current Contact. 



I..ii Magnetic Blow-out Contact. 



U 



Bell Attachment. 



xZX Double Winding -specify ip Differential. 






i^ T*; i"^ ^"^T 



-O- 



Slow Acting. 

DiscTVPE Indicator. ObOisc Invisible. ••Disc Visible. 

Semaphore Type Indicator. P-S-Position. 



>::i ^" i.-i't^ ^^i-i W««E Wound Rotor. 

"i5t "' -o- 



;X! I OR 



a>'\> I u 



i'lM I StatiOn&rv WiuniMfi . L>\i ■ I 



Stationary Windinb. irli,"Hi6H Voltage Windinb. 



Electric Lock- Show Segments for Lever in Normal 
Position . 

(see next page for examples of combinations.) 



Plate VII. 



APPENDIX 



337 



h 



Relays , Indicators and Locks. 

Examples of Combinations. 

D.C RELAY- Neutral- Energized - 

One Independent Front Contact Closed - 
One Independent Back Contact Open . 

OX. RELAY- Polarized -Energized - 

Two Combination Front and Back Neutral Contacts - 
Two Polarized Contacts Closed - 
Two Polarized Contacts Open. 



jj: 



fi 



-o 

M 



-O- 

M 
J.L 

JJ- 



0. C. INDICATOR - Semaphore Type- Energized - 
Three Front Contacts Closed - 
Bell Attachment . 



D.G. INDICATOR- Semaphore Type - Arm Horizontal - 

Energized - Without Contacts . 
NOTE : Indicators (OR repeaters) without contacts should be shown 

with armatures to indicate WHETHER.ENERGtZEO OR DE-ENER- 
GIZED . 

A.C. RELAY- One Energizing Circuit Type (Single Phase) 
Energized -One Front Contact. 



A.C.RELAY-Two Energizing Circuit Type- Energized 
Wire Wound Rotor - 
Two Neutral Front Contacts . 



A.C. relay-Two Energiuno circuit type- energized — 
Wire Wound Rotor — 
Two Polarized Contacts. 

A.C relay-Two Energizing Circuit Type- Energized- 
Stationary Windings — 
One Neutral Front Contact— 
Two 3- Position Contacts . 

O.CJNTERLOCKED REUY. 



D.C. ELECTRIC BELL. 



DESI6NATE RESISTANCE IN OHMS OF ALL D.C. RELAYS, INDICATORS AND LOCKS. 



Plate VIII. 



22 



338 



RAILWAY SIGNALING 



Circuit Controllers Operated by Levers. 

Use either Letter System or Graphic System. 



Levers with Extreme End Position as Normal . 

N- FullIJormal Position of Lever 
B -Normal Indication Position. 
C- Central Position. 
D -Reverse Indication Position. 
R- Full Reverse Position. 



letter 

SYMBOL. 



N B C D R 



-<£>- 

-<NB)- 

-%- 
-^ 

■^ 
-®- 

-®- 
-®- 



GRAPHIC 
SYMBOL. 



< 



^ 



^ 



■^sr 



Levers with Middle Position as Normal. 
N- Normal Position. 
L-Full Reverse Position to the Left. 
B -Indication Position to the Left. 
D -Indication Position to thk Right. 
R-Full Reverse Position to the Right. 



letter 

SYMBOL. 

L 




NOTE: Heavy horizontal lines indicate portion of cycle of lever through which circuit is closed. 



Plate IX. 



APPENDIX 



339 



Circuit Controllers Operated by Signals. 

UPPER QUADRANT. LOWER QUADRANT. 



3 -Position 
Signals. 



^^ 4 Closed at Only. 



y '^ Closed at 



4 4 Closed at 90 Only. 




Closed to 45 



60^70*" OR 
75** Signals. 



i \ Closed at 0° Only. 



4 k 



Closed in Clear 
Position Only. 






45**0nly. '^^ — 



•fr-^ 



-fr-f 



I '^. e o i ' \-/ 

^ ^ Closed 45 to 90 4^^^~~ 



V 



Closed. 
Open. 





Circuit Controller Operated by Locking 
Switch Circuit Controller. Mechanism of a Switch Movement. 



• ) • 



•- >-• 

Bridge Circuit Controller. 



Closed. 
Open. 



Pole Changing Circuit Controller. 

t 

Spring Hand Key or Push Button. 



_iw_ 



Circuit Switch. 



Plate X. 



340 



RAILWAY SIGNALING 



♦J 




Manual Time Release, 
(electric) 






Automatic Time Release, 
(electric) 



T 



Manual Time Release . 

(electro -MECHAN'L.) 




Emersency Release 
(electric) 



rr n 



Floor Push, 



OPEN. closed. 

latch Contact. Track Instrument Contact. 



Knife Switches. 



(> (> 



O 6 6 6 6 o 

Rheostat. Single Pole. Double Pole. Single Pole. Double Pole. 
Single 'F>irow. Double Throw. 

Quick Actins Circuit Controlurs may be Distinguished by the Letter "9' 

— A^/V — J 



Fixed Resistance . 



Variable Resistance. 



Fuse 



ims^ 



Impedance without 
Iron Gore. 



— ^ OOOO'O'O" 

Impedance with 
iron Core 



Condenser. 



Plate XL 



APPENDIX 



341 



Battery. 



^ ^l|l|l|l|l|l|.i 



Rectifier 



A.C.TERMINALS 



D.C.Terminals 
Cells in Multiple Cells in Series 

Specify Type and Number of Cells TRANSFORMERS 

D = Dry Battery 
6 = Gravity »♦ 

P = POTASH »» 

S = Storage '> i-secondary z-or more secondaries 

examples: I6P, lOS, ETC. j r^rv^ j-yQQAijq 

For Grounding Case For Grounding Shield 



iMaflJJMJ I.Q-Q.Q.Q.Q.Q.OJ 

ro'owo'o'o"^ m\ rm 



(M) (6) 



D.C.MOTOP 



D.C.GENERATOR 



A.G. Motor 



Ammeter 



(mMg) (Img) 



A.C.GEHERATOR O.C.--O.C. MOTOR- GENERATOR A.G.-D.C. MOTOR- GENERATOR 



-(A)- -<V)- -^)- XH 



Voltmeter 



WATTMETER TELEPHONE 



Wires Gross 



\ 

) Al 

J L 



® o 

Single Double 

Incandescent Lamp Lightning Arrester Terminals 



Wires Join 



± 



Ground 



" Common " Wire 



Other than " Common "Wire 



Track Circuit Wire 



Direction of Current 



Plate XII. 



342 



RAILWAY SIGNALING 



Explanatory Diagrams 



^ p] p op ^ 'I H 

13J |_J -• POULWE 



SwfLock 
True Meridian Staff Instrument Staff Crane Yard Limits 

SwNAL Control LjMnrs 



^ 



X 



7C^ 



j__z£ 



E 



EXPUNATORY NJfES: 



TB«iH w ucTVNt M »"er,'e"e,tTt. hhk <T'sTiip's«iue,in.2,«,iTc. 

[UTWUO rOAiN OM 'Ef'C MXM n 4S 6(6. siaiM. W.2. 

wcsTvwto THAiM m 'r"c' moiis «t 4S hs. suNikS NO. 2 MO «T 'srcp' SHMtL m.6. 

trreSTWIRD TRAIN ON 'CC' WIK «T 'STtC SKNM.N0.4. 



AiR Pipe and Fittings 



-^- 



■^ 



Expansion Joint Pipe 
Anchor 



Reducers and Bushings 
pont to smaller pipe 



■® o 



Manifold Condenser 



6^ 

Maw Auxiliary 

Reservoirs 



Union Combination Cock 
and Union 

-X 



Plug Cock &obe or 
6ate Valve 



Spligng Chamber Rail Locks 



Runs of Connections 

Pipe- Wire (Mech.) 

Wire Duct 






fiROUND DvWRf 

BRiDSElixai MeScal Ld/^ MACH'« 

BRID6E Coupler 

. Special . Contacts 

J_<|>— ^ - - 



Cof/pRESSED Air 



Pipe-Wire and Duct 



Pipe -Wire and Air 



Duct and Air 



Pipe- Wire, Duct and Air 



Tw««... ij«Trci ® = CoNTAa on Draw Wedges 
T^^«^'^^^= CONTACT ON Time Cuxa. 



3-PosmoN Reuv T 

ooktacts closed to one extreme duop annunciator 
Neutral 







Plate XIII. 



APPENDIX C 

A DEFINITION OF TERMS USED IN RAILWAY SIGNALING^ 

Absolute Block Signaling. — The method of signaling which requires that 
no train be admitted to a block while another train occupies it. 

Acute Angle Crank. — A two-arm crank, the arms of which subtend an 
angle of less than 90 degrees. 

Adjustable Link. — A link, the length of which can be varied. 

Adjusting Screw. — A screw for regulating the relative positions of parts 
of apparatus, or for changing the tension in a wire hne. 

Advance. — The condition of being in an advance position, as a signal in 
relation to a train approaching it. 

Advance Signal. — A signal having the same function as, but placed some 
distance in advance of, the home signal at a block or interlocking station to 
provide a short block section in which a train may be held so as not to 
interfere with the movements of trains in the adjacent block sections. 

Advance Block Signal. — A fixed signal used in connection with a home 
block signal to sub-divide the block ahead. 

Air Gap. — Any space occupied by air in a magnetic or electric circuit. 

Alarm. — Any sound or information intended to give notice of approaching 
danger; a warning sound to arouse attention. 

All-air Interlocking. — An interlocking plant the units of which are oper- 
ated by compressed air only. 

Annunciator. — A device to announce by an audible or visual indication, 
usually in an interlocking or block station, the approach of a train. 

Answer -back Signal. — A signal arranged to give a visual or audible 
indication of the completion of a movement. 

Anti -friction Pipe Carrier. — A pipe carrier in which the movable parts 
carry the pipe without friction. 

Approach Indicator. — An indicator which announces the approach of a 
train. 

Approach Locking. — Electric locking effected by the approach, or released 
by the passing, of a train, through the medium of a track circuit or track 
instrument. 

Arm. — The principal movable part of a semaphore, consisting of a blade 
of wood or metal fastened to a casting which turns on a supporting pivot. 

Arm Casting. — The part of a semaphore arm to which the blade is fas- 
tened, and which contains the bearing and the spectacles for holding the 
glasses through which the night color indications are given. 

Arm Sweep. — The portion of a circle included between any two positions 
of a semaphore arm. 

Aspect.— The position of a signal arm usually considered in its relation 
to the signal mast or a perpendicular thereto. The appearance of a signal 

^Proceedings, Railway Signal Association, 1914. 

343 



344 RAILWAY SIGNALING 

conveying an indication as viewed from the direction of an approaching 
train. 

Audible Signal. — A signal giving an audible indication. 

Automatic. — A term applied to signals which assume their various aspects 
through the exercise of inherent power, as distinguished from those in which 
the changes are made manually. 

Automatic Block Signal. — A block signal having an inherent power of 
motion which is controlled by the passage of a train into, through, and out of, 
the block section which the signal governs, and by the integrity of the track 
within that block. 

Automatic Block Signal System. — A series of consecutive blocks, the use 
of which by trains is controlled by automatic block signals. 

Automatic Block System. — A series of consecutive blocks controlled by 
block signals operated by electric, pneumatic, or other agency, actuated by 
a train or by certain conditions affecting the use of a block. 

Automatic Stop. — An apparatus which, under certain conditions, operates 
in conjunction with an outside agency to stop a train automatically by 
shutting off the motive power, or applying the brakes, or both. 

B 

Back Light. — A light showing through a small glass-covered opening 
in the back of a signal lamp. 

Back Lock. — See Indication Lock. 

Back Locking. — That part of the mechanical locking in a "Standard" 
interlocking machine, which acts back of the tappets. 

Back Spectacle. — A small casting containing a roundel at one end and 
fastened at the other to the semaphore shaft of a signal in such manner as to 
change the visible color of the back light when the signal is moved. 

Back Tail Lever. — The tail lever of a mechanical interlocking machine 
which projects towards the back of the machine. 

Back Wire. — A wire connected to the back tail lever of a mechanical 
interlocking machine and to a signal so that it will insure that the signal 
will assume its normal position when the lever is put normal. 

Balance Lever. — A lever which carries a signal counterweight. 

Banjo Signal. — A term commonly applied to the enclosed disk signal 
because in general appearance it resembles a banjo. 

Banner Signal. — A common name for the clock work signal. 

Battery Chute. — A small receptacle for batteries, commonly made of cast 
iron and sometimes of reinforced concrete or fiber, and usually cylindrical 
in shape, designed to hold two or more battery cells. 

Battery Elevator. — An arrangement of shelves in a supporting frame by 
means of which batteries may be lowered into, held in position in, and raised 
out of, battery chutes. 

Battery Vault. — A term commonly used for battery well. 

Battery Well. — A container for batteries, usually made of reinforced 
concrete. 

Bell Code. — A code in which the strokes of a bell have a predetermined 
significance. 

Bell Crank. — A common name for a crank. 



APPENDIX 345 

Blade. — The extended part of a semaphore arm, which gives the day 
indication. 

Blade Grip. — The part of a semaphore arm to which the blade is secured. 

Block. — A section of track of defined limits, the use of which by trains is 
controlled by block signals. 

Block End. — The end of a block. 

Block Indicator. — An electro-magnetic device controlled by the track 
circuit of a track section, or by track instruments, to indicate, within a 
signal tower, whether or not that track circuit is occupied by a train. 

Block Instrument. — The instrument used in controlled manual block 
signaling to compel the cooperation of the operators at both ends of a block 
in allowing a train to enter from either end. 

Block Length. — The length of a block. 

Block Office. — An office from which the use of a block section is controlled. 

Block Section. — A section of track of defined length, the use of which by 
trains is regulated by a fixed signal, at the entering end on double track, and 
at each end on single track. 

Block Sheet. — The sheet on which movements of trains are recorded at a 
block station. 

Block Signal. — A fixed signal at the entrance to a block section, used to 
give indications regulating the movement of trains into that block. 

Block Signaling. — The method of regulating the movements of railway 
trains, so as to maintain an interval of space between them. 

Block Station. — A place from which block signals are operated. 

Block System. — ^A series of consecutive blocks. 

Bolt Lock. — A lock so arranged that if a switch is not in the proper position 
for a train movement the signal governing that movement cannot be cleared, 
and will prevent a movement of the switch while the signal is in the clear 
position. 

Bond. — A common name for a rail bond. 

Bonding Tube. — A tapered metal tube used for fastening a bond wire to 
a rail. 

Bond Wire. — A common name for a part of a rail bond. 

Bonding Plug. — A piece of metal resembling a rivet in shape and used to 
fasten the wire of a rail bond to a rail. 

Bootleg. — A short piece of the wooden trunking, conduit, or conduit 
encased in concrete, used at the point where a track circuit connection is 
made with the rail to enclose a part of the wire which extends from the rail 
to a battery or relay box. 

Box Crank. — Two or more cranks assembled in a common frame, each 
crank having an independent bearing. 

Boxing. — A wooden covering for pipe or wire lines. 

Box Wheel. — Two or more chain wheels assembled in a common frame, 
each wheel having an independent bearing. A group of chain wheels 
mounted in one frame. 

Bracket Mast. — A signal mast above and supported on the cross piece or 
deck of a bracket post. 

Bracket Post. — An arrangement for supporting two or more signals side by 
side on a single foundation. 



346 RAILWAY SIGNALING 

Bracket Signal. — A signal supported on a bracket mast. 

Bridge Circuit Controller. — A device for connecting and disconnecting 
circuits at the ends of a movable bridge span. 

Bridge Coupler. — A device for engaging and disengaging the interlocking 
connections crossing a movable bridge span. 

Bridge Lock. — A device for locking a movable span of a drawbridge in its 
closed position, so interlocked with the signals governing the approach to 
the bridge that they cannot be cleared unless the bridge is in the closed 
position and locked. 

Bridge Mast. — The upright mast on a signal bridge. 

Bus Bar. — A common conductor on a switchboard or other terminal from 
which taps may be made for taking off current for any purpose. 

Butt End. — A term applied to a jaw or bar the end of which is cut off 
without tang or thread. 

C 

Cab Signal. — An arrangement for producing visual or audible indications 
on moving engines or cars or in the cab of a locomotive to give information 
concerning the condition of the track in advance or of the fixed signals along 
the track. 

Calling-on Arm. — A semaphore arm used to permit a train to move past 
a home signal when the principal arm of the signal has to be left at ''stop." 

Cantilever Bracket Post. — A type of bracket post so constructed that a 
signal mast thereon will be located in proper relation to the track governed. 

Capping. — The covering for trunking. 

Caution. — A term used for the caution indication. See caution indication. 

Caution Card. — A form of written order issued to a train to permit it to 
enter a block which is not clear. 

Caution Signal. — A signal giving a caution indication denoting that a 
train may proceed under some restrictions as to the speed of running. 

Chain Wheel. — A wheel used in transmitting the motion of one part of 
a wire line to another part which extends in a different direction. 

Chain Wheel Stand. — A casting or frame carrying one or more chain 
wheels. 

Channel Pin. — A device in the shape of a truncated cone, in which is cut a 
longitudinal slot, and which is used to fasten a wire to a rail by wedging the 
wire in a hole in the rail. 

Check Locking. — A method of interlocking, electrically, the levers in two 
adjacent interlocking plants to permit train movements between them to be 
made safely against the current of traffic and as the result of cooperation in 
each movement by the operators at the interlocking stations concerned. 

Check Lock Lever. — In an interlocking machine, a separate lever which is 
used for check locking. 

Choke CoU. — A reactance used in connection with lightning arresters and 
placed in series with the line to be protected. 

Choke Coil Lightning Arresters. — A lightning arrester working on the 
choke coil principle. 

Clear (verb). — To cause a signal to assume the aspect which indicates 
that a train may proceed. 



APPENDIX 347 

Clearance Card. — In block signaling, a written order issued by a signal- 
man to authorize a train to enter a block when the signal cannot be cleared. 

Clearance Point. — The point within the angle included between converg- 
ing tracks, at which the clearance lines of those tracks intersect. 

Clear Signal. — A term used to indicate the aspect of a signal which indi- 
cates proceed. 

Clock woik Signal. — A disk signal revolving on a vertical spindle and 
operated by clockwork. 

Common Wire. — A wire which is used to form a part of the paths of 
current in two or more electric circuits. Usually applied to the common 
return wire. 

Compensator. — A device for taking up the effects of temperature so as to 
maintain a constant length in a line of pipe or wire. 

Compound Relay. — A relay having double-wound coils, or separate 
windings, insulated from each other. 

Concrete Bootleg. — A bootleg made from concrete and conduit and used 
in place of wooden trunking, for enclosing the signal wire of a track circuit, 
which leads down to the horizontal wire leading to the battery or relay box. 

Conduit. — A tube of wood, clay, iron or fiber, enclosing electric wires, 
usually underground. 

Contact Rail. — In automatic train-stopping or cab-signaling systems, a 
bar of metal fixed on the ties parallel to the rails of the track in such a way as 
to be rubbed by an electrical conductor carried by the engine or train. 

Control Circuit. — In interlocking, a circuit used to control an operated 
unit or its immediate controlling apparatus ; and in block signaling, a circuit 
used to control a signal at some distance from another signal. 

Controlled Manual Block System. — A block system in which the signals 
are operated manually by mechanisms so constructed that the displaying 
of a clear signal is dependent upon the cooperation of the signalmen at both 
ends of the block, or upon the absence of a train, or, in some cases, certain 
other obstructions, in the block, or both. 

Control Wire. — A wire which carries current from its source to an operated 
unit or its immediate controlling apparatus. 

Convertible Lamp. — A signal lamp equipped for the use of either oil 
burners or bulbs. 

Copper-clad Wire. — An electrical conductor made with a steel center, sur- 
rounded by copper. 

Counterweight. — In a semaphore, a weight so arranged that, in case of 
breakage of the wire, or the pipe controlling the signal, the weight will pull 
the signal to the stop position. 

Counterweight Lever. — A lever on a signal or interlocking machine for 
the support of a counterweight. 

Crank. — A lever, the arms of which form an angle, with the fulcrum at 
the vertex of the angle, which is used to transmit the motion of one part 
of a line of pipe to another part which extends in a different direction. 

Crank Stand. — A frame in which one or more cranks are supported. 

Cross. — The accidental electrical contact of conducting wires. 

Crossing Bar. — A detector bar operated from a lever in an interlocking 
machine and used to prevent the changing of a route over a railway crossing 
while that crossing is occupied by a train. 



348 RAILWAY SIGNALING 

Crossing Gate. — A gate which is lowered on either or both sides of a rail- 
way line across a public highway, to close the highway against traffic while 
a train is passing. 

Crossing Protection. — Any arrangement of signaling or interlocking facili- 
ties designed to prevent collisions at a railway crossing. 

Cross Lock. — A part of the locking, in a machine of the Saxby & Farmer 
type, which is moved by a locking dog in a direction at right angles to the 
movement of the dog. 

Cross Locking. — The arrangement of the cross locks in an interlocking 
machine of the Saxby & Farmer type. 

Crossover. — A short track leading from one to the other of two parallel 
tracks. 

Cross Protection. — The arrangement of electrical conductors and in- 
struments to prevent damage to, and improper operation of, electrical 
apparatus from the effects of a cross, or to allow only such operations as are 
necessary to obviate the possibility of danger. 

Crowfoot Zinc. — A form of zinc plate used in a gravity cell, with a vertical 
stem and several radiating spokes or toes, resembling the foot of a bird. 

Current of Traffic. — The normal movement of trains in a given direction. 

Cut Section. — A track circuit section which requires, at a point within its 
length, the relaying of the effect of a change in its condition. 

Cycle. — In an alternating current a complete change in direction from 
any given value through zero to an equal value in the opposite direction and 
back. 

D 

Danger. — A term formerly used to denote the stop indication of a signal 
(obsolete). 

Dash Pot. — A device, comprising a cylinder in which a fluid acts as a 
cushion for a falling weight attached to a piston within the cylinder. 

Deflecting Bar. — A device which, by means of a curved bar sliding end- 
wise between rollers, transmits the motion of one part of a line of pipe to 
another part which extends in a different direction. 

Derail (noun). — Any device in a fixed location for throwing train wheels 
off the track to prevent them from running into a dangerous situation. 

Derailing Switch. — A switch designed to turn train wheels off the track 
to prevent them from running into a dangerous situation. 

Detector Bar. — A device for preventing the movement of a switch under a 
train, by means of a strip of metal mounted alongside the track rail and 
connected with a lever or an operated unit in such a way that the lever or 
unit is prevented from being moved or unlocked as long as the presence of 
train wheels prevents the bar from being raised. 

Detector Bar Driving Piece. — A device bolted or riveted to a detector bar, 
to which the driving rod is attached. 

Detector Bar Link. — A short link supporting a detector bar, and so pivoted 
on a clip fastened to a track rail that the detector bar in moving longi- 
tudinally must also move upward and above the top of the rail. 

Detector Bar Stop. — A lug fastened to a track rail, on which the detector 
bar rests when its stroke is completed. 



APPENDIX 349 

Differential Relay. — A relay having two sets of coils so arranged that 
each may work in a predetermined relation to the other. 

Disk Signal. — A signal in which the day indications are given by the 
color, or by the absence or presence, of disks. 

Distant Block Signal. — A fixed signal located in the rear of one or more 
home, or home and advance block signals, so controlled by them that it 
gives the indication "prepare to stop," when any controlling signal indicates 
stop, and may give the proceed indications only when all controlling signals 
are clear (or, in some cases, also when they give the caution indication); 
and used to convey information as to the indications of such signals before 
the trains reach the home block signals. 

Distant Indication. — An indication which is conveyed by the aspect of a 
distant signal. 

Distant Signal. — A fixed signal used in connection with a home signal to 
regulate the approach thereto. 

Distant Switch Signal. — A signal used to indicate the position of the 
points of a switch. 

Dog Chart. — A diagrammatic representation of the mechanical locking 
for an interlocking machine ; used as a working plan in making up and fitting 
the locking. 

DoU. — A term used sometimes to designate a short signal post, as the 
bracket mast of a bracket signal. 

Double Jaw. — A special form of jaw for making an intermediate connec- 
tion to a pipe line. 

Double -slip Switch. — A diagonal crossing of two tracks, with switch 
points and frogs so arranged that a train on either track, in either direction, 
can proceed on either track beyond the crossing. 

Double Slot. — A combination of two slots in one case for the control of 
two signal blades on one mast. 

Drawbridge Lock. — A mechanical device to lock in alignment the rails on 
a drawbridge. 

Drop -a way. — The point in the gradual reduction of the amount of current 
flowing through the coils of an electro-magnet at which the amount or value 
of the current is such as to permit the armature to drop away from the cores 
of the magnet coils. 

Dummy. — A bracket mast on a bracket signal bearing no signal arm and 
designed merely to aid by its location relative to the other bracket mast in 
showing to which of two or more tracks a signal applies. 

Dwarf Interlocking Machine. — An interlocking machine of small propor- 
tions, commonly used in the open. 

Dwarf Signal. — A low fixed signal. Similar to and having the same 
functions as a standard home signal. 

E 

Electric Bolt Lock. — An electric lock which insures that the switch and 
the signal governing movements over it are in their proper relative positions 
before either can be moved. 

Electric Bridge Coupler. — A device, one part of which is placed on a draw- 
bridge, with the other part on the abutment, and which is operated, directly 



350 RAILWAY SIGNALING 

or indirectly, by a lever, and is so arranged that a number of circuits passing 
through it can be closed only when the bridge is closed and locked. 

Enclosed Disk Signal. — A signal in which a colored disk is displayed 
behind a glass front in a closed case to form the stop or caution aspect, and 
withdrawn from sight to form the proceed aspect of the signal. 

Electiic Lock. — A device which locks the lever of an interlocking 
machine to prevent its movement, until it is released by an electro- 
magnet. 

Electric Interlocking. — Interlocking in which the operated units are 
operated and controlled by electricity. 

Electric Motor Signal Mechanism. — A signal mechanism operated by an 
electric motor which is controlled by electric apparatus. 

Electric Selector. — An electro-mechanical device by which the electric 
circuit of any one of a number of audible or visible signals or other devices 
may be controlled from a distant point without affecting any of the other 
apparatus or devices. 

Electric Slot. — A device in which the connection between a signal arm and 
its operating mechanism is controlled by an electro-magnet, the connection 
being broken when the magnet is deenergized, and established when the 
parts are in proper mechanical relation and the magnet energized. 

Electric Switch Lock. — An electric lock controlled from a signal cabin and 
attached to the operating connection of an outlying switch to prevent the 
switch from being moved without the knowledge and consent of the signal- 
man in the cabin. 

Electric Train Staff System. — A method of regulating the movements of 
trains in which the possession of a metal staff or a part thereof gives per- 
mission to a train to enter a block, the staffs being kept in machines at the 
ends of the block, which are so electrically locked between adjacent stations 
that only one staff and the sections thereof can be out of the two machines at 
one time. 

Electro-gas Signal. — A semaphore signal worked by compressed carbonic 
acid gas which is controlled by electric apparatus. 

Electrolyte. — The exciting fluid surrounding the plates or elements of an 
electric cell, containing in solution the chemicals which act on the elements 
to produce an electro-chemical current. 

Electro -magnet. — A device comprising one or more coils of insulated wire 
wound around a soft iron or steel core, and depending for its magnetic action 
upon the passage of an electric current through the wire. 

Electro -mechanical Slot. — A device consisting of an electro-magnet with 
levers and rods enclosed in a case and placed on the signal post so that it 
controls the connection between the signal arm and its operating mech- 
anism, and used to prevent a signal from being cleared, or to cause the signal 
to move to the stop position when the route governed by the signal is 
obstructed. 

Electro -pneumatic Interlocking. — Interlocking in which the units are 
operated by compressed air, the application of which is controlled by 
electricity. 

Electro -pneumatic Signals.— Signals which are operated by compressed 
air, th-e application of which is controlled by electricity. 



APPENDIX 351 

Escapement Crank. — A crank, used in a "switch and lock" movement, by 
means of which a single stroke of a lever performs the three operations of 
raising the detector bar and unlocking a switch; moving a switch; and lower- 
ing the detector bar and locking the switch. 



Facing Point Lock. — A lock for an interlocked switch, derail or frog, 
comprising a plunger which engages a lock rod attached to the switch points 
to lock the switch in its normal or reverse position. 

Facing Point Switch. — A switch, the entering end of which is toward an 
approaching train. 

False Clear Signal. — A signal which fails to indicate when the condition of 
the block governed by it is such as to make it unsafe to proceed. 

Fixed Blade Signal. — A signal of fixed aspect, serving as a marker of 
location, having no moving parts and permanently indicating caution or 
stop. 

Fixed Signal. — A permanent signal of fixed location with reference to the 
track, indicating condition affecting the movements of trains, as distin- 
guished from signals given by a motion of the hand or by a flag or lamp. 

Floor Push. — An electric circuit closer fixed in the floor so that a circuit 
may be made by pressure on a plunger. 

Fouling Bar. — A detector bar, placed at or near a fouling point to prevent 
the movement of a unit while a train is on the bar. 

Fouling Point. — See clearance point. 

Foundation. — A fixed support, usually set in the ground, for carriers, 
cranks, compensators, wheels, signals and other like devices. 

F.P.L. — The abbreviation for facing point lock. 

Frequency. — The number of double alternations or periods made by an 
alternating electric current relay, so made that it will act effectively only 
when energized by an alternating current of given frequency. 

Frequency Relay. — An alternating current relay, so made that it will act 
effectively only when energized by an alternating current of the given 
frequency. 

Front Contact. — A part of a relay against which, when the relay magnets 
are energized, the current-carrying portion of the armature is held so as to 
form a continuous path for current. 

Front Rod. — A rod attached to the extreme point of a switch and to which, 
in turn, the lock rod is fastened. 

Front Spectacle. — The spectacle of the semaphore signal which holds the 
blade. See blade casting. 

Full Normal. — The condition of being in, and latched in, the normal posi- 
tion, as applied to the lever of an interlocking machine ; or of being in, and 
locked in, the normal position, as applied to an operated unit. 

Function. — The activity appropriate to the performing or discharging of a 
duty or purpose. See Operated Unit. 

Fusee. — An auxiliary signal consisting of a tube of chemical compound 
which will burn for a predetermined length of time with a colored light, 
generally red or yellow, and which is equipped with a sharp point so that it 
can be thrown to stand upright in the track. 



352 RAILWAY SIGNALING 

G 

Gravity Cell. — A two-fluid primary cell, in which the electrolyi;es are kept 
separate by the difference in their specific gravity, the denser liquid resting 
at the bottom of the jar while the lighter solution stays on top. 

Ground Machine. — An interlocking machine so constructed and arranged 
that it can be placed on the surface of the ground. 

Ground Mast. — A signal mast with its base at or near the surface of the 
ground. Usually supported on a foundation. 

H 

Half -reversed. — The condition of being midway between full normal and 
full reverse as apphed to the lever of an interlocking machine or current 
breaker of a lever or signal. 

Half -reverse Lock. — An electric lock applied to the lever of an interlocking 
machine to prevent the lever from going to its full normal position until 
certain operations have been performed, such as the passing of a train over 
a track circuit, or the operations of a hand release. 

Hand Release. — A device, used in connection with an interlocking 
machine to insure that after a route has been set up or a lever movement 
made, an interval of time must elapse before the route can be changed 
or the lever manipulated. 

Head Block. — One of the end ties on which the points of a switch and the 
switch stand rest. 

Head Rod. — That one of the rods which connect the two points of an 
interlocked switch which is used for throwing the switch. 

High Signal. — A full-sized semaphore mounted on a mast, bridge, building 
or other structure above the level of the top of a car or locomotive. 

High-voltage Signal. — A signal operated by a current of usually 110 volts 
or more. 

Highway Crossing. — The intersection, at the same elevation, of a public 
highway and a railway line. 

Highway Crossing Protection. — An arrangement of one or more highway 
crossing signals. 

Highway Crossing Signal. — An audible or visual signal at a highway 
crossing, designed to warn the users of the highway that it is unsafe to pro- 
ceed over the railway line. 

Hold Clear Attachment. — An attachment to a signal mechanism for 
holding the signal in the clear position. 

Home Block Signal. — A fixed signal, located at the entrance of a 
block. 

Home Interlocking Signal. — A fixed signal at a point at which trains are 
required to stop when the route is not clear. 

Home Signal. — A fixed signal located at the point at which trains are 
required to stop, as distinguished from a distant signal, at which the maxi- 
mum limitation on speed is a response to a caution indication. 

Home Track Circuit. — A track circuit situated between a home signal and 
the advance block signal, which governs the indication of the home signal. 



APPENDIX 353 

Hookgear. — A device by which one lever operates one of two pipe- 
connected signals, depending upon the position of the switch. 

Horizontal Chain Wheel. — A chain wheel, the axis of which is vertical. 
Horizontal Locking. — Locking, a cross section of which lies in a horizontal 
plane. 



Impedance Bond. — A low-resistance bond, making a continuous path for 
return propulsion current, while impeding from one track circuit to another 
the flow of the alternating current used in signaling, and confining the flow 
of that current to one track circuit. 

Impedance Coils. — A term sometimes applied to choking coils or reactance 
coils. 

In Advance of. — Ahead of, as related to an approaching train. 

Indication. — The information or command conveyed by the aspect of a 
visual signal. The information conveyed to the operator of an interlocking 
machine that the movement of an operated unit has been completed, and 
that the unit is in the full normal or full reverse position. 

Indication Lock. — An electric lock fitted to a lever of an interlocking 
machine for the purpose of preventing the return of that lever to its full 
normal latched position until it is released through an impulse of current in 
the lock coils. 

Inductive Bond. — See impedance bond. 

Insulated Rail Joint. — A rail joint in which insulating material is placed 
between the ends of two rails and around the parts of the joint so as to 
prevent the passage of electric current from one rail to the other. 

Interlocking. — An arrangement of switch, lock and signal appliances so 
inter-connected that their movements must succeed each other in a pre- 
determined order. 

Interlocking Machine. — An assemblage of levers and locking in a frame, 
with connections arranged so that the levers can be moved or unlocked only 
in a certain predetermined order, and so that a movement of a lever, or its 
unlocking preparatory to its movement, may be made to lock any or all 
other levers in the frame. 

Interlocking Plant. — An assemblage of switch, lock, and signal appliances 
interlocked. 

Interlocking Relay. — A relay comprising two sets of coils and their 
armatures, so arranged that either armature may be made to prevent the 
other from closing or opening a circuit through a back or front contact. 

Interlocking Signals. — The fixed signals of an interlocking plant. 

Interlocking Signal Oil Pipe. — A pipe which is filled with oil and provided 
with stuffing boxes to prevent the escape of the oil, and containing an 
operating pipe or wire used in mechanical interlocking. 

Interlocking Station. — A place from which an interlocking plant is 
operated. 

Interlocking Unit. — Any signal, switch, derail, lock or crossing bar oper- 
ated separately or in combination with any other constituent part of an 
interlocking system. 



354 RAILWAY SIGNALING 



Jaw. — A forked attachment on a pipe line for making a pivotal connection 
to another pipe line, or to any device. 

Jaw Rod. — A rod having a jaw at either or both of its ends as an integral 
part thereof. 

Johnson Interlocking Machine. — An interlocking machine with the lock- 
ing bars and tappets arranged in a vertical plane beneath it. 

Jumper. — A temporary shunt or short-circuit in a series-connected circuit, 
commonly used in track-circuit work to preserve the continuity of the track 
circuit past a section of track such as a crossing or electrified tracks where 
the wires cannot be suitably insulated. 

Junction Box. — A box to which are run a number of electrical conductors 
for convenient connection, disconnection, or inspection. 



Lag. — The phase difference of one alternating current behind another, or 
of one function of an alternating current behind another, as current and 
voltage. 

Lap Sidings. — An arrangement of two side tracks the ends of which overlap 
each other. 

Latch Block.— A block fastened to the lower extremity of a latch rod, and 
which engages with a square shoulder of the segment or quadrant of a me- 
chanical interlocking machine to hold the lever in position. 

Latch Foot. — The connection on the lower end of the latch rod in a me- 
chanical interlocking machine by means of which the rocking link is actuated. 

Latch Handle. — The part of a lever latch which is grasped by the hand to 
operate the latch. 

Latch Locking. — The arrangement of mechanical locking in which the 
locking bars are driven by means of and through connections to the latches 
of the levers. 

Latch Rod. — The rod extending between the latch handle and the latch 
block on the lever of a mechanical interlocking machine. 

Latch Shoe. — The casting by means of which the latch rod and the latch 
block are held to a lever of a mechanical interlocking machine. 

Lattice Post. — A signal mast or post built up of several uprights which are 
fastened together by diagonal pieces of iron. 

"Lazy Jack" Compensator. — A compensator in which an arm of an 
acute-angle crank is so connected to an arm of an obtuse-angle crank that 
the two connected arms move in the same general direction in overcoming 
the effects of expansion and contraction in lines of pipe connected to the 
opposite arm. 

Leadout. — The arrangement of apparatus by means of which the motions 
of the levers in a mechanical interlocking machine are transmitted to the 
pipe and wire lines outside the interlocking station. 

Lever Latch. — A spring-actuated mechanical device attached to the lever 
of an interlocking machine to hold it in the normal or reversed position. 

Lever Locking. — The arrangement of mechanical locking in which the 
locking is connected directly to the levers. 



APPENDIX 355 

Lever Shoe. — The casting which serves as a bearing for the lever of a 
mechanical interlocking machine, and also as a socket for one or more tail 
levers. 

Line Circuit. — The wires or other conductors in the main line of a circuit. 

Lightning Arrester. — A device to prevent or reduce the possibility of 
damage to electrical apparatus from discharges of lightning. 

Link. — A short piece of l^-in. iron with a sohd jaw at one end and a screw 
jaw at the other. 

"Lock-and-block." — A common name for the controlled manual block 
system. 

Locking. — A mechanical arrangement of locking bars, dogs, and cross- 
locking by means of which the interlocking is effected between the levers of 
an interlocking machine and the order of their movement is determined. 

Locking Bar. — A bar to which locking dogs are attached and which 
extends lengthwise in an arrangement of mechanical locking. 

Locking Bracket. — A bracket which is part of a locking bed and forms one 
of the supports of an arrangement of mechanical locking. 

Locking Dog. — A block which is attached to a locking bar or tappet, by 
means of which the locking between bars is accomplished. 

Locking Filler. — A filler, placed in a spare space of a locking guide to 
prevent the buckling of the locking bar or bars in the adjacent space. 

Locking Frame. — The whole supporting frame of an arrangement of 
mechanical interlocking. 

Locking Plunger. — A plunger of a mechanical locking device which passes 
through an opening in a lock rod. 

Locking Sheet. — A statement in tabular form of the locking operations 
provided for a given interlocking machine. 

Lock Rod. — A rod which is connected to switch points through which a 
locking plunger extends when the points are in the full normal or full reverse 
position. 

"Locking-up" Track Circuit. — A track circuit used to take away the 
unlock when a train passes an advance block signal into the block ahead. 

Lower Quadrant. — One of the quarters of a vertical circle below its 
horizontal axis. 

Lower Quadrant Signal. — A semaphore signal, the arm of which is 
inclined downwardly from the horizontal to give indications. 

M 

Machine Frame. — The support for an interlocking machine. 

Machine Framing. — The frame in an interlocking station on which the 
interlocking machine rests; usually set on a foundation separate from that 
which supports the wall of the building. 

Maintain. — To keep in satisfactory condition. 

Maintainer. — A person whose duty it is to keep signaling apparatus in its 
proper working order. 

Manual Block System. — A block system in which the block signals at a 
block station are moved by hand by an attendant, on information conveyed 
to him from adjacent block stations. 



356 RAILWAY SIGNALING 

Mast. — The upright from which signals are displayed. 

Mechanical Bolt Lock. — A mechanical device connected to a unit in order 
to insure that one or more other units are in their proper relative positions. 

Mechanical Interlocking. — Interlocking in which the units are operated 
manually. 

Mechanical Locking. — See Locking. 

Mercury Contact Relay. — A relay, the armature of which closes one or 
more circuits by making a contact through mercury. 

Mechanical Slot. — A device placed in the connections to a signal which 
requires the movement of more than one operating lever to clear the signal. 

Mechanical Time Lock. — A mechanical device in connection with an 
interlocking signal lever to insure a time interval between throwing the 
signal to stop and moving a derail or switch over which that signal 
governs. 

Mechanical Trip. — A term used to denote a trip — as used in apparatus for 
stopping trains without the intervention of an engineman — ^which is actu- 
ated or controlled by mechanical means as distinguished from apparatus 
in which electricity or magnetism is employed for the same purpose. 

Mechanism. — A general term for any mechanical or power operated 
device for operating a signal or interlocking function or accessory device, 
from a distance. 

Mechanism Case. — The housing for a signal mechanism. 

N 

Neutral Relay. — A relay in which the flow of current in either direction 
through the magnet coils has the same effect on the armature. 

Normal. — The position in which a lever in an interlocking machine stands 
when the corresponding switch or signal is in its normal position. 

Normal Danger. — A term used to express the normal condition of the 
signals in a system in which the indication to proceed is given only upon the 
approach of a train to an unoccupied block. 



Obtuse -angle Crank. — A two-arm crank, the arms of which subtend an 
angle of more than 90 degrees. 

Opposing Train. — A train running in a direction contrary to that of any 
specified train 

Outlying Switch. — A switch not connected with an interlocking plant. 

Overlap. — An extension of track circuit control of the signal at the 
entrance to a block through a portion or all of the block in advance. 

Overstroke. — The excess throw in a pipe or wire line. 



Permissive Block Signaling. — The method of signaling which permits one 
or more trains in the same direction to enter a block section before the last 
preceding train has passed out. 



APPENDIX 357 

"Pick Up." — The point in the gradual increasing of the amount of current 
flowing through the coils of an electro-magnet at which the amount or value 
of the current is such as to overcome the force of gravity on the armature, 
and attract it against the cores of the magnet coils. 

Pinnacle. — A casting, usually ornamental, which is placed on top of a 
signal mast. 

Pipe Adjusting Screw. — A device, used in a pipe line for changing its 
length. 

Pipe Carrier. — A device, comprising a grooved roller working in a stand 
for supporting a pipe line at an interlocking plant in such a manner as to 
permit of its longitudinal movement. 

Pipe Carrier Bearing Plate. — A plate or bar to which pipe carriers are 
fastened. 

Pipe Carrier Side Plate. — A part of a pipe carrier which passes down the 
side of the pipe and is secured to the foundation to form a support for the 
rollers. 

Pipe Carrier Stand. — The supporting frame of a pipe carrier. 

Pipe Connected. — The condition of being connected together by, or 
arranged for operation by means of, a pipe line. 

Pipe Line. — A line of pipe connecting a mechanically operated switch, 
or signal, or other operated unit to its lever in an interlocking machine. 

Pipe Plug. — A plug, consisting of a short section of rod which is inserted 
in and riveted to the contiguous ends of pipe at a joint in a pipe line. 

Pipe Run. — An assemblage of pipe lines with their carriers and founda- 
tions in a common course. 

Pit. — A depression below the floor level of an interlocking station, in 
which part of the leadout apparatus is situated. 

Plunger; — The bar which, by entering a hole in the lock rod, effects the 
locking in a facing point lock. 

Plunger Box. — The casting or guide in which the plunger of a bridge lock 
or bolt lock moves. 

Plunger Casting. — A stand and guide for facing point and bridge lock 
plungers and lock rods. 

Plunger Release Track Circuit. — A track circuit by means of which the 
plunger of a block signal instrument or controlling apparatus is released. 

Plunger Stand. — That part of a facing point lock which is secured at a 
certain fixed distance from the switch point, and through which the plunger 
moves. 

Pneumatic Interlocking Diaphragm Valve. — A valve controlling the 
admission of compressed air from an operating pipe into a switch or signal 
cylinder. 

Pneumatic Interlocking. — Interlocking in which the units are operated 
and controlled by compressed air. 

Point Lug. — A lug bolted to the web of a switch point rail to which the 
switch rods are attached. 

Point Rail. — Either of the two movable rails in a ''split" switch, as dis- 
tinguished from the immovable "stock" rails. 

Polarized Relay. — A relay, the operation of which is controlled by the 
direction of the flow of current through its magnet coils. 



358 RAILWAY SIGNALING 

Polarized Track Circuit. — A track circuit in which the direction of current 
is used to govern the polarity of magnetism in relay magnets for the control- 
ling of apparatus. 

Pole Changer. — A device by which the direction of current flow in an 
electrical circuit may be changed. 

Pole Piece. — That part of the core of an electro-magnet which projects 
beyond the coil, and adjacent to which the armature is placed. 

Polyphase Relay. — A relay designed to respond to polyphase alternating 
current. 

Position Signaling. — A scheme of signaling whereby the information to 
be delivered by a signal is shown by the relative position which the moving 
part of a signal bears to a certain fixed part. 

Pot Signaling. — A low revolving signal, turning on a vertical axis, and 
used either as a switch target for indicating the position of the switch to 
which it is attached, or as a dwarf signal for low-speed movements. 

Power Interlocking. — Interlocking, the units of which are operated by 
some form of power other than manual. 

Preliminary Latch Locking. — Mechanical locking so arranged that the 
locking of a lever to prevent it from being moved in conflict with another 
lever is fully effected before that other lever begins to perform its function. 

Propulsion Bond. — A rail bond which will carry the return current used 
for propulsion purposes on an electric railway. 

Pusher Attachment. — An attachment to electric train-staff apparatus 
designed to protect, in addition to the regular train movement, the move- 
ment of a pusher engine when, after being detached from the rear of the 
train, it is to be run back to its starting point. 

Q 

Quadrant. — The fourth part of a circle. A part of a mechanical inter- 
locking machine which is bolted to the machine frame, and by means of 
which all levers that are locked by another lever in either its normal or 
reversed position, are held locked while that lever is being moved. 

R 

Radial Arm. — A device used for changing the direction of a pipe line. 

Rail Bond. — A metalhc connection between the adjacent ends of con- 
tiguous rails in a track to insure the continuity of that line of rails as an 
electrical conductor. 

Rail Clip. — A metal support bolted or clamped to a rail, for carrying a 
detector bar. 

Railway Crossing. — The intersection at the same elevation of two or 
more railway tracks. 

Ramp. — A bar with an inchned upper surface fixed on the ties of a railway 
track and designed to raise a vertically moving member of a cab-signaHng 
or a train-stopping system depending from a passing locomotive. 

Reactance. — In an alternating current circuit, the component of imped- 
ance or total effect retarding the flow of current which is out of phase with 



APPENDIX 359 

or 90 degrees from the phase of the current. The ohmic effect due to the 
induction in the circuit. 

Reactance Coil. — A coil for producing a difference of phase. A magnetiz- 
ing coil surrounded by a conducting covering or sheathing which opposes 
the passage of rapidly alternating currents less when directly over the 
magnetizing coil than when a short distance from it. 

Rear. — The condition of being behind, as a train in relation to a signal 
which it is approaching. A term used to describe the location of a signal 
which, with reference to another signal, is in its rear when it is in such posi- 
tion as to be passed first by an approaching train. 

Relay. — An electro-magnetic device responsive to direct and alternating 
current which is designed to repeat in one or more electric circuits certain 
effects of changes in, or completion or interruption of the circuit in which it 
is placed. 

Relay Armature. — The movable part of a relay, the positions of which are 
controlled by the condition of the magnet coils according to the presence 
or absence of current therein. 

Relay Post. — A post set in the ground to support a relay box. 

Relay Shelter. — An arrangement for housing a relay. 

Release. — An arrangement for the purpose of releasing either electrically 
or mechanically any apparatus which has previously become locked. 

Release Route Locking. — An arrangement for releasing the route locking 
at an interlocking plant. 

Reverse (verb). — To move a lever or unit in an interlocking machine from 
its normal to the opposite position. 

Right-angle Crank. — A two-arm crank, the arms of which subtend an 
angle of 90 degrees. 

Riser Plate. — An iron plate riveted to a tie plate at a switch and used to 
support the switch points. 

Rocker. — See rocking shaft. 

Rocking Shaft. — A shaft, used in an interlocking plant supported on two 
or more bearings, and rotated about its axis by means of an arm at one end, 
thus transferring the movement to an arm at the other end. A shaft 
which is so supported as to transmit motion by means of a rotary movement 
through less than a circle. 

Rocking Link. — That part of an interlocking machine by means of which 
the latch movement is transmitted to the locking bars. 

Roundel. — A piece of glass used to give the colors to the night indications 
of semaphore signals. 

Roundel Clip. — A device made of rubber for holding a roundel in place 
between the semaphore casting and the roundel ring. 

Roundel Ring. — The ring by means of which a roundel is held in place in 
a spectacle casting. 

Route. — Any path or course which can be taken by a train passing from 
one point to another. 

Route Locking. — The electric locking of switches, drawbridges, etc., in a 
route, or the signals of a conflicting route, to maintain the integrity of a 
route during the movement of a train over it. 



360 RAILWAY SIGNALING 

S 

Screw Jaw. — A jaw fastened by means of a screw connection to the pipe 
or device with which it is used. 

Screw Release. — A form of hand release operated by a screw. 

Selective Despatching System. — A system in which a number of audible 
or visible signals located along a railway line are connected to a telephone, 
telegraph or other circuit, and in which any one of such signals may be 
operated by means of an electric selector without interfering with other 
signals associated with such circuit. 

Selector. — A device by means of which the position of one or more oper- 
ated units may be made to determine which of several others shall be 
operated. 

Selector Coil. — A coil which when energized will attract and hold in place 
an armature which, in turn, will permit a predetermined movement to be 
made. 

Semaphore Arm. — The principal movable part of a semaphore, consisting 
of a blade fastened to a casting which turns on a pivot. 

Semaphore Bearing. — The bearing which supports the pivot of a sema- 
phore arm. 

Semaphore Blade. — That part of the semaphore arm which by its form 
and position gives the day signal indications. 

Semaphore Signal. — A signal in which the indications are given by the 
positions of a movable arm. 

Semi-automatic. — ^The condition in which a part of the operation of a 
mechanism or device is accompUshed through the exercise of inherent power 
of motion. 

Semi-automatic Signal. — A signal which has inherent power to assume 
the stop position after it has been cleared by other means. 

Signal. — A means of conveying information to a train. 

Signal Bracket. — A column or post with an offset support for signal 
masts. 

Signal Bridge. — A bridge which spans one or more railway tracks for the 
purpose of supporting one or more signals. 

Signal Control. — The arrangement through which the operation of a signal 
is governed. 

Signalman. — The attendant at a block or interlocking station. 

Signal Marker Light. — A hght used to distinguish certain fixed signals. 

Signal Mast. — The upright part of a signal which is used to support the 
parts of the signal that give the indication. 

Signal Mechanism. — The apparatus, which in a power-operated signal 
directly operates to change the aspect of the signal. 

Signal Repeater. — An indicator which shows in a cabin the changes in 
position in the arm or movable disk of a fixed signal. 

S. L. M. — The abbreviation for switch and lock movement. 

Slot. — A disconnecting device inserted in the connection between a signal 
arm and its operating mechanism. 

Slotted Signal. — A signal in which the connection from the lever or other 
operating mechanism is controlled by a mechanical or electric slot. 



APPENDIX 361 

Slow-acting Relay. — A relay in which a predetermined time interval is 
made to elapse between the opening of a circuit through the magnet coils 
and the consequent dropping of the armature. 

Slow Board. — A sign to warn the enginemen of trains to reduce speed at a 
certain point. 

Slow-releasing Slot. — An electric slot for an automatic signal, so con- 
structed as to consume an appreciable interval of time between the breaking 
of a circuit and the consequent releasing of the holding mechanism. 

Solenoid Relay. — A relay in which the magnet coils are solenoids with 
movable cores upon which contacts are mounted. 

Smash Signal. — A signal used at particularly dangerous points, such as 
drawbridges, designed to be broken when overrun. 

Solid Jaw. — A special form of jaw rigidly connected to a pipe line. 

Space Interval System. — The method of operating trains so as to main- 
tain certain definite relations of distance between them. 

Spare Lever. — A lever in an interlocking machine to which no unit is 
connected. 

Spare Space. — A lever space in an interlocking rhachine in which there is 
no lever. 

Spark Gap. — The air space or gap through which a disruptive discharge 
passes. 

Special Locking. — The locking on an interlocking machine arranged for 
special conditions. 

Spectacle. — The casting which holds the glass or glasses through which 
the night indications are given on a semaphore signal. 

Speed Control. — The control of an automatic train-stopping apparatus 
by a means which is operative or inoperative according to whether the speed 
of the train is or is not above a certain predetermined rate. 

Spindle Slot. — An electro-mechanical slot attached to the semaphore 
shaft of a signal. 

Staff. — The part of the apparatus, used in the electric train staff system, 
the possession of which gives enginemen permission to enter a block. 

Staff Catcher. — A mast equipped with a device for receiving a staff from 
a moving train or for holding a staff so that it can be picked up by a moving 
train. , 

Standard Code. — The code of interlocking, block signal, and train rules 
adopted by the American Railway Association. 

Stick Relay. — A relay so connected that a circuit through the magnet 
coils, originally closed at an outside point, is held closed through a contact 
of the relay. 

Stock Rail. — Either of the two immovable rails as distinguished from the 
movable ''point" rails in a split switch. 

Straight-arm Compensator. — A compensator which is in the form of 
a straight connection between two parallel parts of a pipe line. 

Suspended Signal. — A signal suspended from an overhead signal bridge, 
or other high structure. 

Switch Adjustment. — An arrangement placed on the front rod of a switch 
or derail so as to provide for taking up any extra motion which the pipe 
line might tend to impart to the switch or derail. 



362 RAILWAY SIGNALING 

Switch Circuit Controller. — A device for opening and closing electric 
circuits of block and interlocking signals, operated by a connecting rod 
attached to the switch points. 

Switch Box. — A common name for a switch circuit controller. 

Switch Indicator. — An electro-magnetic device controlled by a track 
circuit, to indicate whether or not the track section is occupied by a train. 

Switch and Lock Movement. — An arrangement by means of which a 
single stroke of a lever in a mechanical interlocking plant unlocks a switch, 
moves it and locks it again. 

Switch Box. — A circuit controller which is operated in conjunction with 
the movements of a switch and is usually directly connected to the switch 
points. 

Switch Point Lug. — A lug attached to a switch point to which the front 
rod is connected. 



Tag. — A label, usually in the form of a disk or small flat piece of wood, 
fiber, leather, or metal, used to identify wires, wiring connections, or parts 
of apparatus. 

Tail Lever. — The part of the lever of a mechanical interlocking machine 
to which the operating pipe or wire is connected. 

Tang End. — A projection on the end of, and of smaller diameter than, a 
jaw or rod, used to stiffen the joint between the pipe line and the jaw or rod. 

Tappet. — A bar which is operated directly or indirectly by the lever or 
lever latch in an interlocking machine with vertical locking and which actuates 
the locking bars and is locked by them. A pivot or swing-dog which is 
attached to the locking bar in an interlocking machine with horizontal 
locking, and which is actuated or locked by the cross-locking. 

Tappet Circuit Controller. — A circuit controller attached to a tappet and 
usually operated by the movement of a lever latch handle. 

"T" Crank. — A crank with three arms, one of which is at right angles 
with the other two arms. 

Telegraph Block System. — A block system in which the signals are oper- 
ated manually, upon information by telegraph. 

Terminal. — Either end of an electrical circuit, or the device or apparatus 
to which it is attached. The end of a Une or system of railway. 

Three -light Spectacle. — A semaphore spectacle which has three openings 
for light indications. 

Three-position Automatic Block Signals. — A system of automatic block 
signals designed to provide the protection of distant signals without the 
duplication of signal arms usually involved, and in which each signal is so 
arranged that it may be made to present any one of three different aspects. 

Three -position Signal. — A semaphore signal arranged to give three 
different indications. 

Throw Rod. — The rod attached to the head rod of a switch, connecting 
the switch to a switch stand, pipe line, or other operating device. 

Time Interval System. — The method of operation under which trains are 
run where there is no block system. 



APPENDIX 363 

Time Release. — See Time Lock. 

Time Lock. — A device for automatically releasing electric locks or inter- 
locking levers after the expiration of a predetermined time interval. 

Torpedo. — An auxiliary stop or caution signal consisting of an explosive 
cap to be fastened to the top of the rail of a track, and exploded by the pres- 
sure of a wheel of an approaching locomotive or other vehicle. 

Torpedo Placer. — An apparatus for placing torpedoes in position to be 
exploded by the passage of a wheel of a locomotive or other vehicle. 

Torque. — The movement of force causing rotation; the product of the 
force and the distance from the point of application of the force from the 
center of rotation. 

To the Rear of a Signal. — The section of track occupied by a train before 
it has passed a signal. 

Tower. — The common name for the building from which interlocking and 
signals are operated. See Interlocking Station. 

Track Circuit. — An electric circuit of which the rails of a track form a part. 

Track Circuit Locking. — Electric locking which is accomplished through 
the medium of one or more track circuits. 

Track Indicator. — A map-like reproduction of railway tracks, controlled 
by track circuits so arranged as to indicate automatically, for defined sections 
of track, whether or not such sections are occupied. 

Track Instrument. — A lever fixed in relation to the rails of a track so that 
its deflection by passing train wheels may be made to open or close one or 
more electric circuits. 

Track Model. — See Track Indicator. 

Track Relay. — A relay to be placed in and operated by a circuit of which 
the track rails are an integral part. 

Train-order Signal. — A fixed signal used at telegraph offices to indicate 
to a train whether or not it must stop to receive orders. 

Train-order Station. — A station where train orders are received for delivery 
to trains, and where trains may report for orders. 

Transverse Pipe Carrier.^A pipe carrier designed to guide pipe across 
track. 

Trip. — In automatic train-stopping apparatus, the bar, lever, or other 
device, fixed on or near the track or roadway, which when in a certain posi- 
tion trips or releases the apparatus on the vehicle, by which release the stop- 
ping of the vehicle is directly or indirectly effected. 

Trunking. — The wooden casing used to protect both electrical conductor 
wires and those wires used to operate signal arms when they lie on or near 
the surface of the ground. 

Trunnion. — A cylindrical projection on a revolving part for supporting it 
in a bearing. 

Tunnel Signal. — A signal designed to be placed in or to guard a tunnel. 

Two -light Signal Aspect. — A semaphore signal which shows at night at 
least two lights. 

U 

Under Control. — A condition in which an engineer is prepared to stop 
within the distance he can see the track to be clear ahead of him. 



364 RAILWAY SIGNALING 

Up-and-down Rod. — A common name for the movable vertical rod con- 
necting the semaphore signal arm with the operating device at the base of a 
signal mast. 

Upper Quadrant. — One of the quarters of a vertical circle above its hori- 
zontal axis. 

Upper -quadrant Signal. — A semaphore signal the arm of which is inclined 
upwardly from the horizontal to give other than stop indications. 

Universal Link. — The crank arm by means of which motion is transmitted 
from the rocking link to the rocking shaft in an interlocking machine. 

V 

Vane Relay. — A type of alternating-current relay in which a light metal 
disk, or vane, is caused to move the pole pieces of magnets to close contacts 
when the magnets are energized. 

Vertical Locking. — Mechanical Locking arranged in a vertical plane. 

W 

Wheel Stand. — The frame in which chain wheels are supported. 

Wire Adjusting Screw. — A device in a wire line, used for changing its 
length. 

Wire Carrier. — A device, comprising a roller or pulley, supported in a 
frame, used as a support and guide for a wire line. 

Wire Compensator. — A device for automatically keeping the length of a 
wire uniform under variations in temperature. 

Wire Run. — In an interlocking plant, an assemblage of wire lines, with 
their carriers and foundations, in a common course. 

Wood Capping. — The covering for wooden trunking. 



"Z" Armature. — An armature of an electro-magnet shaped like the letter 
Z and used in enclosed disk signals, indicators, and other apparatus. 



INDEX 



Absolute signal, 203 

staff, 190 
AGA highway signals, 315 
Air supply, electro-pneumatic 

system, 78 
Alternating current, block signal- 
ing, 217-270 
double-rail return, 222 
relays, 230 

signal circuits, 237-248 
single-rail return, 218 
interlocking, 121, 125, 132, 141, 
148 
A. P. Block System, 260 
Approach locking, 174 
Arresters, lightning, 162 
Aspect, signal, 8, 206, 325 
Automatic block signaling, double 
track, 198-248 
single track, 249-270 
Automatic stops, 288 



Back locking, 43, 47 
Batteries, 157 

Battery wells and chutes, 160 
Beam light signal, 299 
Bell, crossing, 304 

Block Signal and Train Control 
Board, 7 

signal circuits (see Circuits) 
Bolt lock, 60, 63 
Bonds, impedance, 224 

rail, 152 
Bracket signal, 19, 20, 70, 202 
Brackets, 39 
Bridge couplers, 74 

interlocking, 30 

lock, 75 

signal, 18, 70 
Bureau of Safety, 7 



Cable posts, 160 

Calling-on arm, 73 

Cells, 158 

Center-fed track circuits, 223 

Centrifugal relay, 233, 236 

Channel pin, 154 

Chart, dog, 44 

Check locking, 179 

Chicago, Milwaukee & St. Paul Ry., 

270 
Chutes, battery, 160 
Circuit controllers, indication, 90, 
111, 130, 141, 148 
switch, 126, 215 
Circuits, controUed-manual, 188 
electric interlocking, Federal 
Signal Co., 141 
General Railway Signal Co., 

107, 108, 117-121 
Hall Switch & Signal Co., 

146-148 
Union Switch & Signal Co., 
125-132 
electric locking, 166-180 
electro-pneumatic interlocking, 

92-97 
fouling, 151 
highway crossing signal, 305- 

315 
interlocking (see Electric inter- 
locking) 
signal, automatic block A. C. 
double track two-posi- 
tion, 237-240 
L. I. R. R., 239, 240 
N.Y. N.H.&H.R.R.,242 
N. Y. Subway, 238 
West Jersey & Sea Shore 
R. R., 241 
D. C. double track, curve 
protection, 215, 216 



365 



366 



INDEX 



Circuits, signal, D. C, normal dan- 
ger, 213 
switch protection, 215, 216 
three-position, 211-213 
two-position, 208-211 
single track. General Railway- 
Signal Co., 259-262 
other installations, 262-270 
Chicago, Milwaukee & 

St. Paul Ry., 270 
Cleveland, Southwestern 
& Columbus Ry., 259 
Norfolk & Western Ry., 

267 
Northern Pacific R. R., 

261 
Puget Sound Electric 

Ry., 266 
Washington, Baltimore 
& Annapolis Elect. 
R. R., 252 
Union Switch & Signal Co., 
24^259 
three-position, 240-248 
Cumberland Valley R. R., 

244 
N. Y. Municipal Railway 

Corporation, 246 
Southern Ry., 245 
Union Switch Signal Co., 
243 
signal mechanism, model 2A, 
281, 282 
style "B," 273, 274 
style "T-2," 278 
staff, 190-193 

switch (see Electric interlocking) 
track, steam roads, D. C, 149, 
150 
A. C, 227 
electric roads, 218-220, 222- 
224 
Cleveland, Southwestern & Colum- 
bus Ry., 258 
Clock work time release, 173 
Color-light signals, 11, 288, 291 
Commissions, Interstate, 7 
Public Utilities, 7, 318 
State Railroad, 7, 318 



Compensation table, 55 
Compensators, 51, 56 
Compressor, air, 79 
Controlled-manual block, 187 
Couplers, bridge, 74 
Couplings, 50 
Cranks, horizontal, 57 

vertical, 49 
Cross lock, 39 

protection, 119 
Crossing bars, 66 

bell, 304 
Crossing, single track, 25, 27, 29, 30 

double track, 27, 30 
Cumberland Valley R. R., 244 
Curve protection, 214, 216 
Cut sections, 150 



Deflecting bar, 50 
Departmental system, 3 
Derails, 24, 65 
Detector bar, 60 
Detector locking, 94, 171 
Disc signals, 14, 271 
Distant signal, 10, 24, 201 
Diverging routes, 28, 29, 30 
Division of Safety, I. C. C, 7 
Divisional system, 3 
Dog, 39 

chart, 44-46, 106 
Doll post, 21 
Double-rail return, 222 

track diverging routes, 30 
Drawbridge interlocking, 31 

couplers, 74 
"D" slide valve, 87 
Dwarf signal, 21, 69 

electric, 118 

electro-pneumatic, 98 

position-light, 301 



E 



Electric interlocking. Federal Signal 
Co. system, 135-143 
interlocking machine, 135 
switch machine, 138 



ft 



INDEX 



367 



Electric interlocking, switch ma- 
chine control and indica- 
tion circuits, 141 
General Railway Signal Co, 
system, 102-123 
cross protection, 119 
interlocking machine, 103 
power supply, 102 
signal control, 116 
switch machine, 108 
track diagram, 122 
Hall Switch & Signal Co. sys- 
tem, 144-148 
interlocking machine, 144 
signal circuits, 146 
switch operation, 145 
Union Switch & Signal Co. 
system, 124-133 
interlocking machine, 124 
power supply, 124, 125 
"SS" control, 131 
switch movement, 128 
the indicating system, 127 
Electric locking, 166-180 
Electric train staff, 189 
Electro- mechanical interlocking. 
Federal Signal Co., 143 
General Railway Signal Co., 

123 
Union Switch and Signal Co., 
133 ' 
Electro-mechanical slot, Hall type, 
183 
Union type, 180 
Electro-pneumatic interlocking, 78- 
101 
advantages, 101 
air supply, 78 
detector locking, 94 
electricity, 80 
indication, 90 
interlocking machine, 81 
sequence, 80 
signal mechanism, 98 
signal operation, 99 
"SS" control, 94 
switch mechanism, 87 
switch operation, 94 
End-fed track circuits, 223 



F. P. L., 26 

Facing point lock, 26, 59, 63 
Federal Signal Co., electric inter- 
locking, 135-143 

electro-mechanical, 143 

signal, 285 
Flagman, automatic, 303 
Fouling circuit, 151 
Foundations, 58 
Frequency relay, 233, 236 
Frog, movable point, 64 
Front rod, 162 



G 



Galvanometer relay, 231, 232 
General Railway Signal Co., A. P. 
block system, 259 
automatic stops, 288 
controlled-manual block sys- 
tem, 187 
electric interlocking, 102-123 
electro-mechanical interlocking, 

123 
relays, 234 
semi-automatic signal control, 

115 
signals, 279, 293-296 
switch machines, 108 
Ground signals, 18 



H 



Hall Switch and Signal Co., electric 
interlocking, 144-148 

electro-mechanical slot, 183 

signals, 271, 283, 284 
Hand release, 173 
Hayes derail, 65 
Head rod, 62, 162 
Highway crossing signals, 302 

circuits, 305 
History of signaling, 1 
Hoeschen bell system, 308 
Home signal, 9, 24, 201 
Horizontal crank, 57 

locking, 38 



368 



INDEX 



Illuminated track diagram, 122 
Impedance, 226 
bond, 224 
coil, 220 
Indication circuit controller, 90, 130 
Indication relays, 90, 127 
Indications, blade, 8, 206, 325 
light, 11, 12, 247, 295, 300 
Power Interlocking, Federal Sig- 
nal Co., 141 
General Railway Signal Co., 

106 
Hall Switch & Signal Co., 148 
Union Switch & Signal Co., 
127 
position-light, 300 
Indicators, switch, 214 

tower, 185 
Insulated rail joints, 151 
Insulated rods, 62, 162 
Interlocking, electric systems, Fed- 
eral Signal Co., 135-143 
General Railway Signal Co., 

102-124 
Hall Switch & Signal Co., 

144-148 
Union Switch & Signal Co., 
124-133 
electro-pneumatic, 78-101 
general, 22-35 
mechanical, 36-77 
object of, 22 
Interlocking machines, Electric, Fed- 
eral Signal Co., 135 
General Railway Signal Co., 

103 
Hall Switch & Signal Co., 144 
Union Switch & Signal Co., 
124 
electro-mechanical. Federal Sig- 
nal Co., 143 
General Railway Signal Co., 

123 
Union Switch & Signal Co., 
133 
electro-pneumatic, 81 
general, 36 



Interlocking machines, mechanical, 
horizontal, Saxby and 
Farmer, 36 
Vertical, Johnson, 47 
National, 47 
Stevens, 48 
Style A, 40 
relays, 306 
Interstate Commerce Commission, 7 



Jaws, 52 

Johnson interlocking machine, 47 



Lamp, R. S. A. Semaphore, 72 

Latch, 38 

Latch locking, 39 

Lazy Jack Compensator, 53 

Leadout, 49 

Lightning arresters, 162 

Light signals, 11, 12, 247, 288, 295, 

300 
Location of signals, 19, 23, 199 
Lock, bridge, 75 

electric, 166-180 

F. P. L., 59 

time, 69 
Locking, approach, 174 

check, 179 

electric, 166-180 

horizontal, 36 

route, 176 

Saxby & Farmer, 36 

section, 171 

sectional route, 177 

stick, 177 

style A, 40 

vertical, 40 
Locking bed, 39 

bar, 38, 39, 40 
driver, 38 

details, 41, 44 

shaft, 38 
crank, 38 

sheet, 26 
Lock rod, 63 
Locomotive bell, 304 
L. I. R. R., 239, 240 



INDEX 



369 



M 

Manipulation chart, 35 
Manual block system, 186 
Marker light, 204 
Mechanical interlocking, 36-77 
Morden derail, 66 
Movable bridge couplers, 74 

interlocking, 30, 32 

locks, 74 
point frog, 64 



N 



National interlocking machine, 47 
Neutral relay, 152 
N. Y. Municipal Railway Corpora- 
tion, 246 
N. Y. N. H. & H. R. R., 242 
N. Y. Subway, 238 
Norfolk & Western Ry., 267 
Normal, 24 

Normal clear signals, 208 
Normal danger signals, 213 
Northern Pacific R. R., 261 
Numbering signal posts, 206 

O 

Order of locking, 25 
Organization, 2 
Overlap systems, 203 



Peabody, J. A., 23 
Permissive signaling, 203 
Permissive staff, 194 
Pin valve, electro-pneumatic, 91 
Pipe carriers, 50 
Pipe lines, 55 
Pipes, 50, 52, 79 
Polarized relay, 156 
Polarized track circuits, 209, 213 
Position-light signals, 12, 299 
Posts, cable, 160 
Pouches, staff, 196 
Power interlocking, sequence in, 80 
24 



Power mains, 125 
Preliminary locking, 39 
Puget Sound Electric Ry., 266 
Push button, 85, 133 
Pusher syaff, 197 



Q 



Quick switch, 86 

R 

Radial arm, 57 
Rail bonds, 152 
Rail joints, 151 
Reactance (see Impedance) 
Relays, alternating current, 230-237 

frequency, 233, 236 

indication, 90 

interlocking, 306 

neutral, 152 

polarized, 156 

posts, 160 

stick, 179 
Release, hand, 172 

screw, 172 

slow, 173 

time, 173 
Resistance grid, 219 
Reversed, 24 

Road crossing signals, 302 
Rocker-link, 38 
Rocking shaft, 49 
Rod, front, 162 

head, 62, 162 

insulated, 62 

lock, 63 

tie, 162 
Rosenberg, C. C, 199 
Route locking, 176 
Rules for foremen, 6 

signalmen, 75 

state inspectors, 318 

supervisors, 5 

trainmen, 75 



Saxby and Farmer interlocking 

machine, 36 
Screw release, '173 



370 



INDEX 



Sectional route locking, 177 
Section locking, 171 
Semaphore lamp, 72 
Semaphore signals, 9, 10, 67, 70, 
201-217, 238-245, 249-268, 
272-287 
Sequence in power interlocking, 80 
Setting section, 170 
Shaver, A. G., 3 
Sheet, locking, 26 
Siding protection, 214 
Signal aspect, 8, 206, 325 
batteries, 157 
bridge, 18 
cell, 158 

circuits (see Circuits) 
control, electro-pneumatic, 99, 
100 
electric. Federal Signal Co., 
136 
Hall Switch & Signal Co., 

146, 148 
General Railway Signal 

Co., 115, 118 
Union Switch & Signal Co., 
131 
engineer, 3 
indications, 8 
light indications, 11 
location, 19, 23, 199 
mechanism, color-light, 291 
electro-pneumatic, 275 
Hall disc, 271 
Hoeschen, 308 
light, 288, 291 
model 2A, 279 
position-light, 299 
style ''B", 272 
style "K", 283 
style "L", 284 
style "S", 275 
style "T", 276 
subway, 297 
tunnel, 297 
type ''4", 285 
numbers, 206 

operation, 98, 115, 131, 148 
organization, 2 
Signaling, purpose of, 1, 198, 249 



Signals, disc, 14, 271 

dwarf, 21, 69, 98, 118,301 
light, color, 11, 288, 291 

position, 12, 299 
semaphore, 9, 10, 67, 70, 272- 
287 
Single-rail return, 218 
Single-track crossing, 25-30 

signaling, 249-270 
Slip switch, 64 
S. L. M., 26, 59 
Slot, electro-mechanical, Hall, 183 

Union, 180 
Slow release, 173 
Southern Ry., 245 
South Station, Boston, 78 
Special locking, 26, 39, 42 
''SS" control, 94, 131 
Staff, electric train, 189 

catcher, 194 
Stevens interlocking machine, 48 
Stick locking, 177 

relay, 179 
Stops, automatic, 288 
Stuffing box, 52 
Style A locking, 40 
Subway signals, 238, 246, 294, 297 
Swing bridge couplers, 74 

dog, 39, 43 
Switch, 63 

adjustment, 62 

and lock movement, 26, 59, 87 
box, 215 

circuit controllers, 126, 215 
indicators, 214 

lever wiring, 92, 107, 141, 147 
machine, electro-pneumatic, 87 
Electric, Federal Signal Co., 

138 
General Railway Signal 

Company, 108-114 
Hall Switch & Signal Co., 145 
Union Switch & Signal Co., 
128 
magnets, 88 
movements, 94, 108, 128, 138, 

141 
protection, 214, 216 



INDEX 



371 



Switchboard, 102 
Symbols, R. S. A., 330 



Take siding indicators, 16 

signal, 17 
Tappet bar, 40 
TDB system, 255 

Three-block indication scheme, 206 
Three-position, semaphore signaling, 
202 
signals, 10, 202, 275 
circuits, 211, 240, 259 
Tie rod, 162 
Time element relay, 236 
Time lock, 69 

release, 173 
Tower indicator, 185 
Track batteries, 157 

circuits, steam roads, direct 
current, 149 
alternating current, 227 
electric roads, D. C. propul- 
sion, single-rail return, 
218 
double-rail return, 222 
A. C. propulsion, 227 
diagram, 34, 122 
Traihng point crossover, 29 
Train staff, 189 
Transformers, 222, 228 
Transmission line, 217 
Trunking, 161, 163 
Two-position, distant signal, 10, 201, 
208 
home signal, 9, 201, 208 
polarized track circuits, 209 
semaphore signaUng, 201 
signal circuits, 208, 237 
Type "F" interlocking machine, 124 



U 

Unbalancing of current, 225 
Union Switch & Signal Co., Electric, 
Type "F" system, 124-133 
electro-mechanical interlocking, 

133 
electro-mechanical slot, 180 
electro-pneumatic interlocking, 

78-101 
flagman, 303 
relays, 155, 230 
signals, 272, 292, 294, 297 
single track systems, TDB 
system, 249 
Universal link, 38 



Vane relay, 230 
Vertical crank, 49 
locking, 40, 43 

W 

Washington, Baltimore & Annapolis 

Electric R. R., 252 
Wells, battery, 160 
West Jersey & Seashore R. R., 241 
Wigwag signal, 303 
Wire compensator, 56 
Wiring diagram (see Circuits) 



X 



X" springs, 94 



Y" springs, 94 



Z armature, 271 



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